Anything performed without the direction of the Vedas is called vikarma, or unauthorized or sinful work. Therefore, one should always take direction from the Vedas to be saved from the reaction of work. As one has to work in ordinary life by the direction of the state, one similarly has to work under direction of the supreme state of the Lord. Such directions in the Vedas are directly manifested from the breathing of the Supreme Personality of Godhead. It is said, asya mahato bhūtasya niśvasitam etad yad ṛg-vedo yajur-vedaḥ sāmavedo 'tharvāṅgirasaḥ. "The four Vedas-namely the Ṛg Veda, Yajur Veda, Sāma Veda, and Atharva Veda—are all emanations from the breathing of the great Personality of Godhead." (Bṛhad-āraṇyaka Upaniṣad 4.5.11) The Lord, being omnipotent, can speak by breathing air, for as it is confirmed in the Brahma-saṁhitā, the Lord has the omnipotence to perform through each of His senses the actions of all other senses. In other words, the Lord can speak through His breathing, and He can impregnate by His eyes. In fact, it is said that He glanced over material nature and thus fathered all living entities. After creating or impregnating the conditioned souls into the womb of material nature, He gave His directions in the Vedic wisdom as to how such conditioned souls can return home, back to Godhead.
(Bhagavad-Gita-----3:15-----purport).

The entire cosmic manifestations, moving and nonmoving, are manifested by different activities of Kṛṣṇa's energy. In the material existence we create different relationships with different living entities who are nothing but Kṛṣṇa's marginal energy; under the creation of prakṛti some of them appear as our father, mother, grandfather, creator, etc., but actually they are parts and parcels of Kṛṣṇa. As such, these living entities who appear to be our father, mother, etc., are nothing but Kṛṣṇa. In this verse the word dhātā means "creator." Not only are our father and mother parts and parcels of Kṛṣṇa, but the creator, grandmother and grandfather, etc., are also Kṛṣṇa. Actually any living entity, being part and parcel of Kṛṣṇa, is Kṛṣṇa. All the Vedas, therefore, aim only toward Kṛṣṇa. Whatever we want to know through the Vedas is but a progressive step toward understanding Kṛṣṇa. That subject matter which helps us purify our constitutional position is especially Kṛṣṇa. Similarly, the living entity who is inquisitive to understand all Vedic principles is also part and parcel of Kṛṣṇa and as such is also Kṛṣṇa. In all the Vedic mantras the word oṁ, called praṇava, is a transcendental sound vibration and is also Kṛṣṇa. And because in all the hymns of the four Vedas-Sāma, Yajur, Ṛg and Atharva-the praṇava, or oṁkāra, is very prominent, it is understood to be Kṛṣṇa.
(Bhagavad-Gita-----9:17-----purport).

A learned scholar who has studied the Vedas perfectly and has information from authorities like Lord Caitanya and who knows how to apply these teachings can understand that Kṛṣṇa is the origin of everything in both the material and spiritual worlds, and because he knows this perfectly he becomes firmly fixed in the devotional service of the Supreme Lord. He can never be deviated by any amount of nonsensical commentaries or by fools. All Vedic literature agrees that Kṛṣṇa is the source of Brahmā, Śiva and all other demigods. In the Atharva Veda (Gopāla-tāpanī Upaniṣad 1.24) it is said, yo brahmāṇaṁ vidadhāti pūrvaṁ yo vai vedāṁś ca gāpayati sma kṛṣṇaḥ: "It was Kṛṣṇa who in the beginning instructed Brahmā in Vedic knowledge and who disseminated Vedic knowledge in the past." Then again the Nārāyaṇa Upaniṣad (1) says, atha puruṣo ha vai nārāyaṇo 'kāmayata prajāḥ sṛjeyeti: "Then the Supreme Personality Nārāyaṇa desired to create living entities." The Upaniṣad continues, nārāyaṇād brahmā jāyate, nārāyaṇād prajāpatiḥ prajāyate, nārāyaṇād indro jāyate, nārāyaṇād aṣṭau vasavo jāyante, nārāyaṇād ekādaśa rudrā jāyante, nārāyaṇād dvādaśādityāḥ: "From Nārāyaṇa, Brahmā is born, and from Nārāyaṇa the patriarchs are also born. From Nārāyaṇa, Indra is born, from Nārāyaṇa the eight Vasus are born, from Nārāyaṇa the eleven Rudras are born, from Nārāyaṇa the twelve Ādityas are born." This Nārāyaṇa is an expansion of Kṛṣṇa.
(Bhagavad-Gita-----10:8-----purport).

In this verse there are some significant words, just like veda-yajñādhyayanaiḥ, which refers to studying Vedic literature and the subject matter of sacrificial regulations. Veda refers to all kinds of Vedic literature, such as the four Vedas (Ṛg, Yajur, Sāma and Atharva) and the eighteen Purāṇas, the Upaniṣads and the Vedānta-sūtra. One can study these at home or anywhere else. Similarly, there are sūtras-Kalpa-sūtras and Mīmāṁsā-sūtras—for studying the method of sacrifice. Dānaiḥ refers to charity which is offered to a suitable party, such as those who are engaged in the transcendental loving service of the Lord—the brāhmaṇas and the Vaiṣṇavas. Similarly, "pious activities" refers to the agni-hotra and the prescribed duties of the different castes. And the voluntary acceptance of some bodily pains is called tapasya. So one can perform all these—can accept bodily penances, give charity, study the Vedas, etc.—but unless he is a devotee like Arjuna, it is not possible to see that universal form. Those who are impersonalists are also imagining that they are seeing the universal form of the Lord, but from Bhagavad-gītā we understand that the impersonalists are not devotees. Therefore they are unable to see the universal form of the Lord.
(Bhagavad-Gita-----11:48-----purport).

Originally the Veda is one. But Śrīla Vyāsadeva divided the original Veda into four, namely Sāma, Yajur, Ṛg, Atharva, and then again they were explained in different branches like the Purāṇas and the Mahābhārata. Vedic language and the subject matter are very difficult for ordinary men. They are understood by the highly intelligent and self-realized brāhmaṇas. But the present age of Kali is full of ignorant men. Even those who are born by a brāhmaṇa father are, in the present age, no better than the śūdras or the women. The twice-born men, namely the brāhmaṇas, kṣatriyas and vaiśyas, are expected to undergo a cultural purificatory process known as saṁskāras, but because of the bad influence of the present age the so-called members of the brāhmaṇa and other high-order families are no longer highly cultured. They are called the dvija-bandhus, or the friends and family members of the twice-born. But these dvija-bandhus are classified amongst the śūdras and the women. Śrīla Vyāsadeva divided the Vedas into various branches and subbranches for the sake of the less intelligent classes like the dvija-bandhus, śūdras and women.
(Srimad Bhagavatam-----1:3:21-----purport).

There is no difference also between the Vedic mantras and what is explained in the Purāṇas and Itihāsa. According to Śrīla Jīva Gosvāmī, it is mentioned in the Mādhyandina-śruti that all the Vedas, namely the Sāma, Atharva, Ṛg, Yajur, Purāṇas, Itihāsas, Upaniṣads, etc., are emanations from the breathing of the Supreme Being. The only differences are that the Vedic mantras mostly begin with praṇava oṁkāra and that it requires some training to pronounce the metrical accent, without which the mantras cannot be successfully chanted. Although Śrīla Sūta Gosvāmī was a preacher of the first order, he did not bother much about the metrical pronunciation of the Vedic mantras. But that does not mean that Śrīmad-Bhāgavatam is of less importance than the Vedic mantras. On the contrary, it is the ripened fruit of all the Vedas, as stated before. Besides that, the most perfectly liberated soul, Śrīla Śukadeva Gosvāmī, is absorbed in the studies of the Bhāgavatam, although he is already self-realized. Śrīla Sūta Gosvāmī is following his footsteps, and therefore his position is not the least less important because he was not expert in chanting Vedic mantras with metric pronunciation, which depends more on practice than actual realization. Realization is more important than parrotlike chanting.
(Srimad Bhagavatam-----1:4:13-----purport).

Formerly there was only the Veda of the name Yajur, and the four divisions of sacrifices were there specifically mentioned. But to make them more easily performable, the Veda was divided into four divisions of sacrifice, just to purify the occupational service of the four orders. Above the four Vedas, namely Ṛg, Yajur, Sāma, and Atharva, there are the Purāṇas, the Mahābhārata, Saṁhitās, etc., which are known as the fifth Veda. Śrī Vyāsadeva and his many disciples were all historical personalities, and they were very kind and sympathetic toward the fallen souls of this age of Kali. As such, the Purāṇas and Mahābhārata were made from related historical facts which explained the teaching of the four Vedas. There is no point in doubting the authority of the Purāṇas and Mahābhārata as parts and parcels of the Vedas. In the Chāndogya Upaniṣad (7.1.4), the Purāṇas and Mahābhārata, generally known as histories, are mentioned as the fifth Veda. According to Śrīla Jīva Gosvāmī, that is the way of ascertaining the respective values of the revealed scriptures.
(Srimad Bhagavatam-----1:4:19-----purport).

The living beings are created by the creator Brahmā, and just to maintain the created living being progressively towards the path back to Godhead, the system of performing sacrifice is also created by him. The system is that living beings live on the produce of grains and vegetables, and by eating such foodstuff they get vital power of the body in the shape of blood and semen, and from blood and semen one living being is able to create other living beings. But the production of grains, grass, etc. becomes possible by rain, and this rain is made to shower properly by performance of recommended sacrifices. Such sacrifices are directed by the rites of the Vedas, namely Sāma, Yajur, Ṛg and Atharva. In the Manu-smṛti it is recommended that by offerings of sacrifice on the altar of the fire, the sun-god is pleased. When the sun-god is pleased, he properly collects water from the sea, and thus sufficient clouds collect on the horizon and rains fall. After sufficient rains fall, there is sufficient production of grains for men and all animals, and thus there is energy in the living being for progressive activity. The mlecchas, however, make plans to install slaughterhouses for killing bulls and cows along with other animals, thinking that they will prosper by increasing the number of factories and live on animal food without caring for performance of sacrifices and production of grains. But they must know that even for the animals they must produce grass and vegetables, otherwise the animals cannot live. And to produce grass for the animals, they require sufficient rains. Therefore they have to depend ultimately on the mercy of the demigods like the sun-god, Indra and Candra, and such demigods must be satisfied by performances of sacrifice.
(Srimad Bhagavatam-----1:16:20-----purport).

As we have already quoted above from the Bhakti-rasāmṛta-sindhu of Rūpa Gosvāmī, even mundane things, if dovetailed in the service of the Lord Śrī Kṛṣṇa, are accepted as transcendental. For example, the epics or the histories of Rāmāyaṇa and Mahābhārata, which are specifically recommended for the less intelligent classes (women, śūdras and unworthy sons of the higher castes), are also accepted as Vedic literature because they are compiled in connection with the activities of the Lord. Mahābhārata is accepted as the fifth division of the Vedas after its first four divisions, namely Sāma, Yajur, Ṛg and Atharva. The less intelligent do not accept Mahābhārata as part of the Vedas, but great sages and authorities accept it as the fifth division of the Vedas. Bhagavad-gītā is also part of the Mahābhārata, and it is full of the Lord's instruction for the less intelligent class of men. Some less intelligent men say that Bhagavad-gītā is not meant for householders, but such foolish men forget that Bhagavad-gītā was explained to Arjuna, a gṛhastha (family man), and spoken by the Lord in His role as a gṛhastha. So Bhagavad-gītā, although containing the high philosophy of the Vedic wisdom, is for the beginners in the transcendental science, and Śrīmad-Bhāgavatam is for graduates and postgraduates in the transcendental science. Therefore literatures like Mahābhārata, the, purāṇas and similar other literatures which are full of the pastimes of the Lord, are all transcendental literatures, and they should be discussed with full confidence in the society of great devotees.
(Srimad Bhagavatam-----2:3:14-----purport).

In the Padma Purāṇa, Uttara-khaṇḍa, there is a full description of the yoga-pīṭha, or the particular place where the Lord is in audience to His eternal devotees. In that yoga-pīṭha, the personifications of religion, knowledge, opulence and renunciation are all seated at the lotus feet of the Lord. The four Vedas, namely Ṛk, Sāma, Yajur and Atharva, are present there personally to advise the Lord. The sixteen energies headed by Caṇḍa are all present there. Caṇḍa and Kumuda are the first two doorkeepers, at the middle door are the doorkeepers named Bhadra and Subhadra, and at the last door are Jaya and Vijaya. There are other doorkeepers also, named Kumuda, Kumudākṣa, Puṇḍarīka, Vāmana, Śaṅkukarṇa, Sarvanetra, Sumukha, etc. The Lord's palace is well decorated and protected by the above-mentioned doorkeepers.
(Srimad Bhagavatam-----2:9:16-----purport).

The nine principal ṛṣis, or sages, are Marīci, Atri, Aṅgirā, Pulastya, Pulaha, Kratu, Bhṛgu, Vasiṣṭha and Atharvā. All these ṛṣis are most important, and Brahmā desired that the nine daughters already born of Kardama Muni be handed over to them. Here two words are used very significantly-yathā-śīlam and yathā-ruci. The daughters should be handed over to the respective ṛṣis, not blindly, but according to the combination of character and taste. That is the art of combining a man and woman. Man and woman should not be united simply on the consideration of sex life. There are many other considerations, especially character and taste. If the taste and character differ between the man and woman, their combination will be unhappy. Even about forty years ago, in Indian marriages, the taste and character of the boy and girl were first of all matched, and then they were allowed to marry. This was done under the direction of the respective parents. The parents used to astrologically determine the character and tastes of the boy and girl, and when they corresponded, the match was selected: "This girl and this boy are just suitable, and they should be married." Other considerations were less important. The same system was also advised in the beginning of the creation by Brahmā: "Your daughters should be handed over to the ṛṣis according to taste and character."
(Srimad Bhagavatam-----2:24:15-----purport).

The word śāstra refers to the scriptures, particularly the Vedic books of knowledge. The Vedas-Sāma, Yajur, Ṛg and Atharva—and any other books deriving knowledge from these Vedas are considered Vedic literatures. Bhagavad-gītā is the essence of all Vedic knowledge, and therefore it is the scripture whose instructions should be especially accepted. In this essence of all śāstras, Kṛṣṇa personally advises that one give up all other duties and surrender unto Him (sarva-dharmān parityajya mām ekaṁ śaraṇaṁ vraja (B.G.18:66).
One should be initiated into following the principles of śāstra. In offering initiation, our Kṛṣṇa consciousness movement asks one to come to the conclusion of śāstra by taking the advice of the supreme speaker of the śāstra, Kṛṣṇa, forgetting the principles of the materialistic way of life. Therefore the principles we advise are no illicit sex, no intoxication, no gambling and no meat-eating. These four types of engagement will enable an intelligent person to get free from the materialistic life and return home, back to Godhead.
(Srimad Bhagavatam-----6:5:20-----purport).

In Satya-yuga there was only one Veda, not four. Later, before the beginning of Kali-yuga, this one Veda, the Atharva Veda (or, some say, the Yajur Veda), was divided into four—Sāma, Yajur, Ṛg and Atharva—for the facility of human society. In Satya-yuga the only mantra was oṁkāra (oṁ tat sat). The same name oṁkāra is manifest in the mantra Hare Kṛṣṇa, Hare Kṛṣṇa, Kṛṣṇa Kṛṣṇa, Hare Hare/ Hare Rāma, Hare Rāma, Rāma Rāma, Hare Hare. Unless one is a brāhmaṇa, one cannot utter oṁkāra and get the desired result. But in Kali-yuga almost everyone is a śūdra, unfit for pronouncing the praṇava, oṁkāra. Therefore the śāstras have recommended the chanting of the Hare Kṛṣṇa mahā-mantra. Oṁkāra is a mantra, or mahā-mantra, and Hare Kṛṣṇa is also a mahā-mantra. The purpose of pronouncing oṁkāra is to address the Supreme Personality of Godhead, Vāsudeva (oṁ namo bhagavate vāsudevāya). And the purpose of chanting the Hare Kṛṣṇa mantra is the same. Hare: "O energy of the Lord!" Kṛṣṇa: "O Lord Kṛṣṇa!" Hare: "O energy of the Lord!" Rāma: "O Supreme Lord, O supreme enjoyer!" The only worshipable Lord is Hari, who is the goal of the Vedas (vedaiś ca sarvair aham eva vedyaḥ (B.G.15:15). By worshiping the demigods, one worships the different parts of the Lord, just as one might water the branches and twigs of a tree. But worshiping Nārāyaṇa, the all-inclusive Supreme Personality of Godhead, is like pouring water on the root of the tree, thus supplying water to the trunk, branches, twigs, leaves and so on. In Satya-yuga people knew how to fulfill the necessities of life simply by worshiping Nārāyaṇa, the Supreme Personality of Godhead. The same purpose can be served in this age of Kali by the chanting of the Hare Kṛṣṇa mantra, as recommended in the Bhāgavatam. Kīrtanād eva kṛṣṇasya mukta-saṅgaḥ paraṁ vrajet (S.B.12:3:51). Simply by chanting the Hare Kṛṣṇa mantra, one becomes free from the bondage of material existence and thus becomes eligible to return home, back to Godhead.
(Srimad Bhagavatam-----9:14:48-----purport).