The members of the four divisions of human life, namely the brahmacārī, the gṛhastha, the vānaprastha and the sannyāsī, are all meant to become perfect yogīs or transcendentalists. Since human life is not meant for our enjoying sense gratification like the animals, the four orders of human life are so arranged that one may become perfect in spiritual life. The brahmacārīs, or students under the care of a bona fide spiritual master, control the mind by abstaining from sense gratification. A brahmacārī hears only words concerning Kṛṣṇa consciousness; hearing is the basic principle for understanding, and therefore the pure brahmacārī engages fully in harer nāmānukīrtanam—chanting and hearing the glories of the Lord. He restrains himself from the vibrations of material sounds, and his hearing is engaged in the transcendental sound vibration of Hare Kṛṣṇa, Hare Kṛṣṇa.
(Bhagavad-Gita----4:26----purport).

"The vow of brahmacarya is meant to help one completely abstain from sex indulgence in work, words and mind-at all times, under all circumstances, and in all places." No one can perform correct yoga practice through sex indulgence. Brahmacarya is taught, therefore, from childhood, when one has no knowledge of sex life. Children at the age of five are sent to the guru-kula, or the place of the spiritual master, and the master trains the young boys in the strict discipline of becoming brahmacārīs. Without such practice, no one can make advancement in any yoga, whether it be dhyāna, jñāna or bhakti. One who, however, follows the rules and regulations of married life, having a sexual relationship only with his wife (and that also under regulation), is also called a brahmacārī. Such a restrained householder brahmacārī may be accepted in the bhakti school, but the jñāna and dhyāna schools do not even admit householder brahmacārīs. They require complete abstinence without compromise. In the bhakti school, a householder brahmacārī is allowed controlled sex life because the cult of bhakti-yoga is so powerful that one automatically loses sexual attraction, being engaged in the superior service of the Lord.
(Bhagavad-Gita----6:13-14----purport).

In the Vedic system of knowledge, students, from the very beginning, are taught to vibrate oṁ and learn of the ultimate impersonal Brahman by living with the spiritual master in complete celibacy. In this way they realize two of Brahman's features. This practice is very essential for the student's advancement in spiritual life, but at the moment suchbrahmacārī (unmarried celibate) life is not at all possible. The social construction of the world has changed so much that there is no possibility of one's practicing celibacy from the beginning of student life. Throughout the world there are many institutions for different departments of knowledge, but there is no recognized institution where students can be educated in the brahmacārī principles. Unless one practices celibacy, advancement in spiritual life is very difficult.
(Bhagavad-Gita----8:11----purport).

One has to study the Vedas under the guidance of the spiritual master and undergo many austerities and penances while living under his care. A brahmacārī has to live in the home of the spiritual master just like a servant, and he must beg alms from door to door and bring them to the spiritual master. He takes food only under the master's order, and if the master neglects to call the student for food that day, the student fasts. These are some of the Vedic principles for observing brahmacarya.
After the student studies the Vedas under the master for some time—at least from from age five to twenty—he may become a man of perfect character. Study of the Vedas is not meant for the recreation of armchair speculators, but for the formation of character. After this training, the brahmacārī is allowed to enter into household life and marry. When he is a householder, he has to perform many sacrifices so that he may achieve further enlightenment. He must also give charity according to the country, time and candidate, discriminating among charity in goodness, in passion and in ignorance, as described in Bhagavad-gītā. Then after retiring from household life, upon accepting the order of vānaprastha, he undergoes severe penances—living in forests, dressing with tree bark, not shaving, etc. By carrying out the orders of brahmacarya, householder life, vānaprastha and finally sannyāsa, one becomes elevated to the perfectional stage of life. Some are then elevated to the heavenly kingdoms, and when they become even more advanced they are liberated in the spiritual sky, either in the impersonal brahmajyoti or in the Vaikuṇṭha planets or Kṛṣṇaloka. This is the path outlined by Vedic literatures.
(Bhagavad-Gita----8:28----purport).

Sacrifice is another item to be performed by the householders, because sacrifices require a large amount of money. Those in other orders of life, namely brahmacarya, vānaprastha and sannyāsa, have no money; they live by begging. So performance of different types of sacrifice is meant for the householders. They should perform agni-hotra sacrifices as enjoined in the Vedic literature, but such sacrifices at the present moment are very expensive, and it is not possible for any householder to perform them. The best sacrifice recommended in this age is called saṅkīrtana-yajña. This saṅkīrtana-yajña, the chanting of Hare Kṛṣṇa, Hare Kṛṣṇa, Kṛṣṇa Kṛṣṇa, Hare Hare/ Hare Rāma, Hare Rāma, Rāma Rāma, Hare Hare, is the best and most inexpensive sacrifice; everyone can adopt it and derive benefit. So these three items, namely charity, sense control and performance of sacrifice, are meant for the householder.
Then svādhyāya, Vedic study, is meant for brahmacarya, or student life. Brahmacārīs should have no connection with women; they should live a life of celibacy and engage the mind in the study of Vedic literature for cultivation of spiritual knowledge. This is called svādhyāya.
Tapas, or austerity, is especially meant for the retired life. One should not remain a householder throughout his whole life; he must always remember that there are four divisions of life—brahmacarya, gṛhastha, vānaprastha and sannyāsa.
(Bhagavad-Gita----16:1-3----purport).

The varṇas are, so to speak, classifications of different occupations, and āśrama-dharma is gradual progress on the path of self-realization. Both are interrelated, and one is dependent on the other. The main purpose of āśrama-dharma is to awaken knowledge and detachment. The brahmacārī āśrama is the training ground for the prospective candidates. In this āśrama it is instructed that this material world is not actually the home of the living being. The conditioned souls under material bondage are prisoners of matter, and therefore self-realization is the ultimate aim of life. The whole system of āśrama-dharma is a means to detachment. One who fails to assimilate this spirit of detachment is allowed to enter into family life with the same spirit of detachment. Therefore, one who attains detachment may at once adopt the fourth order, namely, renounced, and thus live on charity only, not to accumulate wealth, but just to keep body and soul together for ultimate realization. Household life is for one who is attached, and the vānaprastha and sannyāsa orders of life are for those who are detached from material life. The brahmacārī-āśrama is especially meant for training both the attached and detached.
(Srimad Bhagavatam----1:9:26----purport).

To give charity is one of the householder's main functions, and he should be prepared to give in charity at least fifty percent of his hard-earned money. A brahmacārī, or student, should perform sacrifices, a householder should give charity, and a person in the retired life or in the renounced order should practice penances and austerities. Those are the general functions of all the āśramas, or orders of life on the path of self-realization. In the brahmacārī life the training is sufficiently imparted so that one may understand that the world as property belongs to the Supreme Lord, the Personality of Godhead.
(Srimad Bhagavatam----1:9:27----purport).

In order to award the highest benefit of human life, the varṇāśrama system trains the follower to adopt the vow of celibacy beginning from the order of brahmacārī. The brahmacārī life is for students who are educated to follow strictly the vow of celibacy. Youngsters who have had no taste of sex life can easily follow the vow of celibacy, and once fixed in the principle of such a life, one can very easily continue to the highest perfectional stage, attaining the kingdom of the three-fourths energy of the Lord. It is already explained that in the cosmos of three-fourths energy of the Lord there is neither death nor fear, and one is full of the blissful life of happiness and knowledge. A householder attached to family life can easily give up such a life of sex indulgence if he has been trained in the principles of the life of a brahmacārī.
(Srimad Bhagavatam----2:6:20----purport).

The brahmacāri, or a boy from the age of five years, especially from the higher castes, namely from the scholarly parents (the brāhmaṇas), the administrative parents (the kṣatriyas), or the mercantile or productive parents (the vaiśyas), is trained until twenty-five years of age under the care of a bona fide guru or teacher, and under strict observance of discipline he comes to understand the values of life along with taking specific training for a livelihood. The brahmacārī is then allowed to go home and enter householder life and get married to a suitable woman. But there are many brahmacārīs who do not go home to become householders but continue the life of naiṣṭhika-brahmacārīs, without any connection with women. They accept the order of sannyāsa, or the renounced order of life, knowing well that combination with women is an unnecessary burden that checks self-realization.
(Srimad Bhagavatam----2:7:6----purport).

Since sex desire is very strong at a certain stage of life, the guru may allow the brahmacārī to marry; this license is given to a brahmacārī who is unable to continue the way of naiṣṭhika-brahmacarya, and such discriminations are possible for the bona fide guru. A program of so-called family planning is needed. The householder who associates with woman under scriptural restrictions, after a thorough training of brahmacarya, cannot be a householder like cats and dogs. Such a householder, after fifty years of age, would retire from the association of woman as a vānaprastha to be trained to live alone without the association of woman. When the practice is complete, the same retired householder becomes a sannyāsī, strictly separate from woman, even from his married wife. Studying the whole scheme of disassociation from women, it appears that a woman is a stumbling block for self-realization, and the Lord appeared as Nārāyaṇa to teach the principle of womanly disassociation with a vow in life.
(Srimad Bhagavatam----2:7:6----purport).

During student life the brahmacārīs were given full instructions about the importance of the human form of life. Thus the basic education was designed to encourage the student in becoming free from family encumbrances. Only students unable to accept such a vow in life were allowed to go home and marry a suitable wife. Otherwise, the student would remain a permanent brahmacārī, observing complete abstinence from sex life for his whole life. It all depended on the quality of the student's training. We had the opportunity to meet an avowed brahmacārī in the personality of our spiritual master, Oṁ Viṣṇupāda Śrī Śrīmad Bhaktisiddhānta Gosvāmī Mahārāja. Such a great soul is called a naiṣṭhika-brahmacārī.
(Srimad Bhagavatam----3:12:42----purport).

Of the four orders of human society—the student, or brahmacārī order, the householder, or gṛhastha order, the retired, or vānaprastha order, and the renounced, or sannyāsī order—the householder is on the safe side. The bodily senses are considered plunderers of the fort of the body. The wife is supposed to be the commander of the fort, and therefore whenever there is an attack on the body by the senses, it is the wife who protects the body from being smashed. The sex demand is inevitable for everyone, but one who has a fixed wife is saved from the onslaught of the sense enemies. A man who possesses a good wife does not create a disturbance in society by corrupting virgin girls. Without a fixed wife, a man becomes a debauchee of the first order and is a nuisance in society—unless he is a trained brahmacārī, vānaprastha or sannyāsī. Unless there is rigid and systematic training of thebrahmacārī by the expert spiritual master, and unless the student is obedient, it is sure that the so-called brahmacārī will fall prey to the attack of sex. There are so many instances of falldown, even for great yogīs like Viśvāmitra. A gṛhastha is saved, however, because of his faithful wife. Sex life is the cause of material bondage, and therefore it is prohibited in three āśramas and is allowed only in the gṛhastha-āśrama. The gṛhastha is responsible for producing first-quality brahmacārīs, vānaprasthas and sannyāsīs.
(Srimad Bhagavatam----3:14:20----purport).

Here are some descriptions of a brahmacārī-yogī. In the morning, the first duty of a brahmacārī seeking spiritual elevation is huta-hutāśana, to offer sacrificial oblations to the Supreme Lord. Those engaged in brahmacarya cannot sleep until seven or nine o'clock in the morning. They must rise early in the morning, at least one and a half hours before the sun rises, and offer oblations, or in this age, they must chant the holy name of the Lord, Hare Kṛṣṇa. As referred to by Lord Caitanya, kalau nāsty eva nāsty eva nāsty eva gatir anyathā: there is no other alternative, no other alternative, no other alternative, in this age, to chanting the holy name of the Lord. The brahmacārī must rise early in the morning and, after placing himself, should chant the holy name of the Lord. From the very features of the sage, it appeared that he had undergone great austerities; that is the sign of one observing brahmacarya, the vow of celibacy. If one lives otherwise, it will be manifest in the lust visible in his face and body. The word vidyotamānam indicates that the brahmacārī feature showed in his body. That is the certificate that one has undergone great austerity in yoga. A drunkard or smoker or sex-monger can never be eligible to practice yoga. Generally yogīs look very skinny because of their not being comfortably situated, but Kardama Muni was not emaciated, for he had seen the Supreme Personality of Godhead face to face. Here the word snigdhāpāṅgāvalokanāt means that he was fortunate enough to see the Supreme Lord face to face. He looked healthy because he had directly received the nectarean sound vibrations from the lotus lips of the Personality of Godhead. Similarly, one who hears the transcendental sound vibration of the holy name of the Lord, Hare Kṛṣṇa, also improves in health. We have actually seen that many brahmacārīs and gṛhasthas connected with the International Society for Krishna Consciousness have improved in health, and a luster has come to their faces. It is essential that a brahmacārī engaged in spiritual advancement look very healthy and lustrous. The comparison of the sage to an unpolished gem is very appropriate. Even if a gem just taken from a mine looks unpolished, the luster of the gem cannot be stopped. Similarly, although Kardama was not properly dressed and his body was not properly cleansed, his overall appearance was gemlike.
(Srimad Bhagavatam----3:21:45-47----purport).

The principle of brahmacarya is celibacy. There are two kinds of brahmacārīs. One is called naiṣṭhika-brahmacārī, which means one who takes a vow of celibacy for his whole life, whereas the other, the upakurvāṇa-brahmacārī, is a brahmacārī who takes the vow of celibacy up to a certain age. For example, he may take the vow to remain celibate up to twenty-five years of age; then, with the permission of his spiritual master, he enters married life. Brahmacarya is student life, the beginning of life in the spiritual orders, and the principle of brahmacarya is celibacy. Only a householder can indulge in sense gratification or sex life, not a brahmacārī. Svāyambhuva Manu requested Kardama Muni to accept his daughter, since Kardama had not taken the vow of naiṣṭhika-brahmacarya. He was willing to marry, and the suitable daughter of a high royal family was presented.
(Srimad Bhagavatam----3:22:14----purport).

A brahmacārī practices celibacy, controlling his sex life. One cannot enjoy unrestricted sex life and practice yoga; this is rascaldom. So-called yogīs advertise that one can go on enjoying as one likes and simultaneously become a yogī, but this is totally unauthorized. It is very clearly explained here that one must observe celibacy. Brahmacaryam means that one leads his life simply in relationship with Brahman, or in full Kṛṣṇa consciousness. Those who are too addicted to sex life cannot observe the regulations which will lead them to Kṛṣṇa consciousness. Sex life should be restricted to persons who are married. A person whose sex life is restricted in marriage is also called a brahmacārī.
(Srimad Bhagavatam----3:28:4----purport).

The system of brahmacarya has been current since the birth of Brahmā. A section of the population, especially male, did not marry at all. Instead of allowing their semen to be driven downwards, they used to lift the semen up to the brain. They are called ūrdhva-retasaḥ, those who lift up. Semen is so important that if, by the yogic process, one can lift the semen up to the brain, he can perform wonderful work—one's memory is enabled to act very swiftly, and the duration of life is increased. Yogīs can thus perform all kinds of austerity with steadiness and be elevated to the highest perfectional stage, even to the spiritual world. Vivid examples of brahmacārīs who accepted this principle of life are the four sages Sanaka, Sanandana, Sanātana and Sanat-kumāra, as well as Nārada and others.
(Srimad Bhagavatam----4:8:1----purport).

In the upper grades (in the life of birds and bees) there is sex, but the insects and animals do not know how to actually enjoy sex life. In the human form of life, however, there is full knowledge of how to enjoy sex. Indeed, there are many so-called philosophers who give directions on how to enjoy sex life. There is even a science called kāma-śāstra, which is the science of sex. In human life there are also such divisions as brahmacarya, gṛhastha, vānaprastha and sannyāsa. There is no sex life except in the gṛhastha, or householder, āśrama. The brahmacārī is not allowed any sex, a vānaprastha voluntarily refrains from sex, and the sannyāsī is completely renounced. The karmīs do not practicebrahmacarya, vānaprastha or sannyāsa life, for they are very much interested in gṛhastha life. In other words, a human being is very much materially inclined. Indeed, all living entities are materially inclined. They prefer gṛhastha life because there is a concession for sex. The karmīs think the other statuses of life are worse than animal life, for animals also have sex, whereas the brahmacārī, vānaprastha and sannyāsī completely give up sex. The karmīs, therefore, abhor these orders of spiritual life.
(Srimad Bhagavatam----4:25:38----purport).

The great sage Nārada Muni was a naiṣṭhika-brahmacārī—that is, he never had sex life. He was consequently an ever-green youth. Old age, jarā, could not attack him. The invalidity of old age can overcome an ordinary man, but Nārada Muni was different. Taking Nārada Muni to be an ordinary man, the daughter of Time confronted him with her lusty desire. It requires great strength to resist a woman's attraction. It is difficult for old men, and what to speak of young. Those who live as brahmacārīs must follow in the footsteps of the great sage Nārada Muni, who never accepted the proposals of Jarā. Those who are too much sexually addicted become victims of jarā, and very soon their life-span is shortened. Without utilizing the human form of life for Kṛṣṇa consciousness the victims of jarā die very soon in this world.
(Srimad Bhagavatam----4:27:21----purport).

The human form of life is especially meant for getting out of the bondage of fruitive activities, but as long as one is forgetful of his life's mission and acts like an ordinary animal—eating, sleeping, mating and defending—he must continue his conditioned life of material existence. Such a life is called svarūpa-vismṛti, forgetfulness of one's real constitutional position. Therefore in Vedic civilization one is trained in the very beginning of life as a brahmacārī. A brahmacārī must execute austerities and refrain from sex indulgence. Therefore if one is completely trained in the principles of brahmacarya, he generally does not enter household life. He is then called a naiṣṭhika-brahmacārī, which indicates total celibacy. King Parīkṣit was thus astonished that the great King Priyavrata, although trained in the principles of naiṣṭhika-brahmacarya, entered household life.
(Srimad Bhagavatam----5:1:1----purport).

Tapaḥ is explained in the smṛti-śāstra as follows: manasaś cendriyāṇāṁ ca aikāgryaṁ paramaṁ tapaḥ. "Complete control of the mind and senses and their complete concentration on one kind of activity is called tapaḥ." Our Kṛṣṇa consciousness movement is teaching people how to concentrate the mind on devotional service. This is first-class tapaḥ. Brahmacarya, the life of celibacy, has eight aspects: one should not think of women, speak about sex life, dally with women, look lustfully at women, talk intimately with women or decide to engage in sexual intercourse, nor should one endeavor for sex life or engage in sex life. One should not even think of women or look at them, to say nothing of talking with them. This is called first-class brahmacarya. If a brahmacārī or sannyāsī talks with a woman in a secluded place, naturally there will be a possibility of sex life without anyone's knowledge. Therefore a complete brahmacārī practices just the opposite. If one is a perfect brahmacārī, he can very easily control the mind and senses, give charity, speak truthfully and so forth. To begin, however, one must control the tongue and the process of eating.
(Srimad Bhagavatam----6:1:13-14----purport).

The natural instinct of a woman is to enjoy the material world. She induces her husband to enjoy this world by satisfying his tongue, belly and genitals, which are called jihvā, udara and upastha. A woman is expert in cooking palatable dishes so that she can easily satisfy her husband in eating. When one eats nicely, his belly is satisfied, and as soon as the belly is satisfied the genitals become strong. Especially when a man is accustomed to eating meat and drinking wine and similar passionate things, he certainly becomes sexually inclined. It should be understood that sexual inclinations are meant not for spiritual progress but for gliding down to hell. Thus Kaśyapa Muni considered his situation and lamented. In other words, to be a householder is very risky unless one is trained and the wife is a follower of her husband. A husband should be trained at the very beginning of his life. Kaumāra ācaret prājño dharmān bhāgavatān iha (S.B.7:6:1). During the time of brahmacarya, or student life, a brahmacārī should be taught to be expert in bhāgavata-dharma, devotional service. Then when he marries, if his wife is faithful to her husband and follows him in such life, the relationship between husband and wife is very desirable. However, a relationship between husband and wife without spiritual consciousness but strictly for sense gratification is not at all good. It is said in Śrīmad-Bhāgavatam (12.2.3) that especially in this age, Kali-yuga, dām-patye 'bhirucir hetuḥ: the relationship between husband and wife will be based on sexual power. Therefore householder life in this Kali-yuga is extremely dangerous unless both the wife and husband take to Kṛṣṇa consciousness.
(Srimad Bhagavatam----6:1:18:40----purport).