In Bhagavad-gītā sexual intercourse for begetting children is accepted as righteous. A person sexually inclined for simple sense gratification, however, is unrighteous. In Diti's appeal to her husband for sex, it was not exactly that she was afflicted by sex desires, but she desired sons. Since she had no sons, she felt poorer than her co-wives. Therefore Kaśyapa was supposed to satisfy his bona fide wife.
(Srimad Bhagavatam------3:14:11-------purport).

The conditions for having good progeny in society are that the husband should be disciplined in religious and regulative principles and the wife should be faithful to the husband. In Bhagavad-gītā (7.11) it is said that sexual intercourse according to religious principles is a representation of Kṛṣṇa consciousness. Before engaging in sexual intercourse, both the husband and the wife must consider their mental condition, the particular time, the husband's direction, and obedience to the demigods. According to Vedic society, there is a suitable auspicious time for sex life, which is called the time for garbhādhāna. Diti neglected all the principles of scriptural injunction, and therefore, although she was very anxious for auspicious children, she was informed that her children would not be worthy to be the sons of a brāhmaṇa. There is a clear indication herein that a brāhmaṇa's son is not always a brāhmaṇa. Personalities like Rāvaṇa and Hiraṇyakaśipu were actually born of brāhmaṇas, but they were not accepted as brāhmaṇas because their fathers did not follow the regulative principles for their birth. Such children are called demons, or Rākṣasas. There were only one or two Rākṣasas in the previous ages due to negligence of the disciplinary methods, but during the age of Kali there is no discipline in sex life. How, then, can one expect good children? Certainly unwanted children cannot be a source of happiness in society, but through the Kṛṣṇa consciousness movement they can be raised to the human standard by chanting the holy name of God. That is the unique contribution of Lord Caitanya to human society.
(Srimad Bhagavatam------3:14:38-------purport).

The mental situation at the time of sex life may then be transferred into the womb of the wife, and good children can come out of that pregnancy. Here is a special reference to Devahūti's bodily features. Because she had become skinny, she feared that her body might have no attraction for Kardama. She wanted to be instructed how to improve her bodily condition in order to attract her husband. Sexual intercourse in which the husband is attracted to the wife is sure to produce a male child, but sexual intercourse based on attraction of the wife for the husband may produce a girl. That is mentioned in the Āyur-veda. When the passion of the woman is greater, there is a chance of a girl's being born. When the passion of the man is greater, then there is the possibility of a son. Devahūti wanted the passion of her husband to be increased by the arrangement mentioned in the kāma-śāstra. She wanted him to instruct her in that way, and she also requested that he arrange for a suitable house because the hermitage in which Kardama Muni was living was very simple and completely in the mode of goodness, and there was less possibility of passion's being aroused in his heart.
(Srimad Bhagavatam------3:23:11-------purport).

Then when we are awake we shall see that everything is simply a dream. But factually, although the demons say that life is a dream, they are very expert in enjoying this dream. And so, instead of acquiring knowledge, they become more and more implicated in their dreamland. They conclude that as a child is simply the result of sexual intercourse between man and woman, this world is born without any soul. For them it is only a combination of matter that has produced the living entities, and there is no question of the existence of the soul. As many living creatures come out from perspiration and from a dead body without any cause, the whole living world has come out of the material combinations of the cosmic manifestation. Therefore material nature is the cause of this manifestation, and there is no other cause.
(Bhagavad-Gita-----16:8--------purport).

A young man and a young woman meet, and the senses drive the young man to see her, to touch her and to have sexual intercourse. In the beginning this may be very pleasing to the senses, but at the end, or after some time, it becomes just like poison. They are separated or there is divorce, there is lamentation, there is sorrow, etc. Such happiness is always in the mode of passion. Happiness derived from a combination of the senses and the sense objects is always a cause of distress and should be avoided by all means.
(Bhagavad-Gita-----18:38--------purport).

The heavenly pleasure for the conditioned soul is sexual pleasure, and this pleasure is tasted by the genitals. The woman is the object of sexual pleasure, and both the sense perception of sexual pleasure and the woman are controlled by the Prajāpati, who is under the control of the Lord's genitals. The impersonalist must know from this verse that the Lord is not impersonal, for He has His genitals, on which all the pleasurable objects of sex depend. No one would have taken the trouble to maintain children if there were no taste of heavenly nectar by means of sexual intercourse. This material world is created to give the conditioned souls a chance for rejuvenation for going back home, back to Godhead, and therefore generation of the living being is necessary for upkeep of the purpose of creation. Sexual pleasure is an impetus for such action, and as such one can even serve the Lord in the act of such sexual pleasure. The service is counted when the children born of such sexual pleasure are properly trained in God consciousness. The whole idea of material creation is to revive the dormant God consciousness of the living entity.
(Srimad Bhagavatam------2:10:26-------purport).

The ass is an animal who is celebrated as the greatest fool, even amongst the animals. The ass works very hard and carries burdens of the maximum weight without making profit for itself. Footnote. The ass is generally engaged by the washerman, whose social position is not very respectable. And the special qualification of the ass is that it is very much accustomed to being kicked by the opposite sex. When the ass begs for sexual intercourse, he is kicked by the fair sex, yet he still follows the female for such sexual pleasure. A henpecked man is compared, therefore, to the ass. The general mass of people work very hard, especially in the age of Kali. In this age the human being is actually engaged in the work of an ass, carrying heavy burdens and driving ṭhelā and rickshaws. The so-called advancement of human civilization has engaged a human being in the work of an ass. The laborers in great factories and workshops are also engaged in such burdensome work, and after working hard during the day, the poor laborer has to be again kicked by the fair sex, not only for sex enjoyment but also for so many household affairs.
(Srimad Bhagavatam------2:3:19-------purport).

The whole idea of material creation is to revive the dormant God consciousness of the living entity. In forms of life other than the human form, sexual pleasure is prominent without any motive of service for the mission of the Lord. But in the human form of life the conditioned soul can render service to the Lord by creating progeny suitable for the attainment of salvation. One can beget hundreds of children and enjoy the celestial pleasure of sexual intercourse, provided he is able to train the children in God consciousness. Otherwise begetting children is on the level of the swine. Rather, the swine is more expert than the human being because the swine can beget a dozen piglets at a time, whereas the human being can give birth to only one at a time. So one should always remember that the genitals, sexual pleasure, the woman and the offspring are all related in the service of the Lord, and one who forgets this relationship in the service of the Supreme Lord becomes subjected to the threefold miseries of material existence by the laws of nature. Perception of sexual pleasure is there even in the body of the dog, but there is no sense of God consciousness. The human form of life is distinct from that of the dog by the perception of God consciousness.
(Srimad Bhagavatam------2:10:26-------purport).

The human being is more passionate than the animals, and thus the sex life of the human being is more irregular. The animals have their due time for sexual intercourse, but the human being has no regular time for such activities. The human being is endowed with a higher, advanced stage of consciousness for getting relief from the existence of material miseries, but due to his ignorance he thinks that his higher consciousness is meant for advancing in the material comforts of life. Thus his intelligence is misused in the animal propensities—eating, sleeping, defending and mating—instead of spiritual realization. By advancing in material comforts the human being puts himself into a more miserable condition, but, illusioned by the material energy, he always thinks himself happy, even while in the midst of misery. Such misery of human life is distinct from the natural comfortable life enjoyed even by the animals.
(Srimad Bhagavatam------3:10:26-------purport).

Lust for sexual intercourse is so strong that it appears herein that Brahmā could not be dissuaded from his determination in spite of the appeal by his great sons like Marīci. Therefore, the great sons began to pray to the Supreme Lord for the good sense of Brahmā. It is only by the grace of the Supreme Lord that one can be protected from the allurement of lusty material desires. The Lord gives protection to devotees who are always engaged in His transcendental loving service, and by His causeless mercy He forgives the accidental fall of a devotee. Therefore, sages like Marīci prayed for the mercy of the Lord, and their prayer was fruitful.
(Srimad Bhagavatam------3:12:32-------purport).

It appears from the talks of Kaśyapa with his wife that he was a worshiper of Lord Śiva, and although he knew that Lord Śiva would not be pleased with him for such a forbidden act, he was obliged to act by his wife's desire, and thus he offered his obeisances unto fate. He knew that the child born of such untimely sexual intercourse would certainly not be a good child, but could not protect himself because he was too obligated to his wife. In a similar case, however, when Ṭhākura Haridāsa was tempted by a public prostitute at the dead of night, he avoided the allurement because of his perfection in Kṛṣṇa consciousness. That is the difference between a Kṛṣṇa conscious person and others. Kaśyapa Muni was greatly learned and enlightened, and he knew all the rules and regulations of systematic life, yet he failed to protect himself from the attack of sex desire. Ṭhākura Haridāsa was not born of a brāhmaṇa family, nor was he himself brāhmaṇa, yet he could protect himself from such an attack due to his being Kṛṣṇa conscious. Ṭhākura Haridāsa used to chant the holy name of the Lord three hundred thousand times daily.
(Srimad Bhagavatam------3:14:31-------purport).

It is said that household attraction resides in the wife because sex is the center of household life: yan maithunādi-gṛhamedhi-sukhaṁ hi tuccham (S.B.7:9:45). A materialistic person, making his wife the center of attraction, works very hard day and night. His only enjoyment in material life is sexual intercourse. Therefore karmīs are attracted to women as friends or wives. Indeed, they cannot work without sex. Under the circumstances the wife is compared to a whirlwind, especially during her menstrual period. Those who strictly follow the rules and regulations of householder life engage in sex only once a month, at the end of the menstrual period. As one looks forward to this opportunity, his eyes are overwhelmed by the beauty of his wife. Thus it is said that the whirlwind covers the eyes with dust. Such a lusty person does not know that all his material activities are being observed by different demigods, especially the sun-god, and are being recorded for the karma of one's next body. Astrological calculations are called jyoti-śāstra. Because the jyoti, or effulgence, in the material world comes from the different stars and planets, the science is called jyoti-śāstra, the science of the luminaries.
(Srimad Bhagavatam------5:13:4-------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).

One should strictly follow the regulative principles, namely no illicit sex, no meat-eating, no intoxication and no gambling, and in this way one should make progress in spiritual life. If an unfit person sentimentally accepts vairāgya or takes sannyāsa but at the same time remains attached to women, he is in a very dangerous position. His renunciation is called markaṭa-vairāgya, or renunciation like that of a monkey. The monkey lives in the forest, eats fruit and does not even cover itself with a cloth. In this way it resembles a saint, but the monkey always thinks of female monkeys and sometimes keeps dozens of them for sexual intercourse. This is called markaṭa-vairāgya. Therefore one who is unfit should not accept the renounced order of life. One who accepts the order of sannyāsa but again becomes agitated by sensual disturbances and talks privately with women is called dharma-dhvajī or dharma-kalaṅka, which means that he brings condemnation upon the religious order. Therefore one should be extremely careful in this connection. Śrīla Bhaktisiddhānta Sarasvatī Ṭhākura explains the word markaṭa to mean "restless." A restless person cannot be steady; therefore he simply wanders about, gratifying his senses.
(Sri Caitanya Caritamrta-------3:2:120---------purport).

One should not enter the temple of the Deity without first making some sound. (4) One should not offer any foodstuff to the Deity which has been seen by dogs or other lower animals. (5) One should not break silence while worshiping. (6) One should not pass urine or evacuate while engaged in worshiping. (7) One should not offer incense without offering some flower. (8) Useless flowers without any fragrance should not be offered. (9) One should not fail to wash his teeth very carefully every day. (10) One should not enter the temple directly after sexual intercourse. (11) One should not touch a woman during her menstrual period. (12) One should not enter the temple after touching a dead body. (13) One should not enter the temple wearing garments of red or blue color or garments which are unwashed. (14) One should not enter the temple after seeing a dead body. (15) One should not pass air within the temple. (16) One should not be angry within the temple. (17) One should not enter the temple after visiting a crematorium. (18) One should not belch before the Deity. So, until one has fully digested his food, he should not enter the temple. (19) One should not smoke marijuana, or gañjā. (20) One should not take opium or similar intoxicants.
(Nectar of Devotion).