"The Vedas clearly enjoin that cows should not be killed. Therefore any Hindu, whoever he may be, does not indulge in cow killing. In the Vedas and Puranas there are injunctions declaring that if one can revive a living being, he can kill it for experimental purposes [in the ritual]. Therefore the great sages sometimes killed old animals, and by chanting Vedic hymns they again brought them to life for protection. The killing and rejuvenation of such old and invalid animals was not truly killing but an act of great benefit. Formerly there were great powerful brahmanas who could make such experiments using Vedic hymns, but now, because of Kali-yuga, brahmanas are not so powerful. Therefore the killing of cows and bulls for rejuvenation is forbidden. 'In this age of Kali, five acts are forbidden: the offering of a horse in sacrifice, the offering of a cow in sacrifice, the acceptance of the [renounced] order of sannyasa, the offering of oblations of flesh to the forefathers, and a man's begetting children in his brother's wife.' Since you Mohammedans [and others] cannot bring killed animals back to life, you are responsible for killing them. Therefore you are going to hell; there is no way for your deliverance."

Caitanya Mahaprabhu, Caitanya Ccaritamrita, Adi-lila 17:159-165

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