If one wishes to engage in devotional service to the Supreme in order to be purified and to reach the goal of life—the transcendental loving service of God—then one should find out what the Lord desires of him. One who loves Kṛṣṇa will give Him whatever He wants, and he avoids offering anything which is undesirable or unasked. Thus meat, fish and eggs should not be offered to Kṛṣṇa. If He desired such things as offerings, He would have said so. Instead He clearly requests that a leaf, fruit, flowers and water be given to Him, and He says of this offering, "I will accept it." Therefore, we should understand that He will not accept meat, fish and eggs. Vegetables, grains, fruits, milk and water are the proper foods for human beings and are prescribed by Lord Kṛṣṇa Himself. Whatever else we eat cannot be offered to Him, since He will not accept it. Thus we cannot be acting on the level of loving devotion if we offer such foods.
(BHAGAVAD-GITA------9:26-----PURPORT).

The brāhmaṇas and Vaiṣṇavas know what to eat, and by their personal example they do not eat anything which is not offered first to the Supreme Personality of Godhead. They eat only prasāda, or remnants of the food offered to the Lord. The kṣatriyas, vaiśyas and śūdras should eat only kṛṣṇa-prasāda, which is afforded them by the mercy of the brāhmaṇas. They cannot open slaughterhouses and eat meat, fish or eggs or drink liquor, or earn money for this purpose without authorization. In the present age, because society is not guided by brahminical instruction, the whole population is only absorbed in sinful activities. Consequently, everyone is deservedly being punished by the laws of nature. This is the situation in this age of Kali.
(SRIMAD BHAGAVATAM------4:22:46------PURPORT).

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