Book of Enoch
Chapter VII
And all the others together with them took unto themselves wives, and each chose for himself one, and they began to go in unto them and to defile themselves with them, and they taught them charms and enchantments, and the cutting of roots, and made them acquainted with plants.
And they began to sin against birds, and beasts, and reptiles, and fish, and to devour one another's flesh, and drink the blood.