Book of Jasher Chapter 2:17-25
And Lamech, the son of Methusael, became related to Cainan by marriage, and he took his two daughters for his wives, and Adah conceived and bare a son to Lamech, and she called his name Jabal. And she again conceived and bare a son, and called his name Jubal; and Zillah, her sister, was barren in those days and had no offspring. For in those days the sons of men began to trespass against God, and to transgress the commandments which he had commanded to Adam, to be fruitful and multiply in the earth. And some of the sons of men caused their wives to drink a draught that would render them barren, in order that they might retain their figures and whereby their beautiful appearance might not fade. And when the sons of men caused some of their wives to drink, Zillah drank with them. And the child-bearing women appeared abominable in the sight of their husbands as widows, whilst their husbands lived, for to the barren ones only they were attached. And in the end of days and years, when Zillah became old, the Lord opened her womb. And she conceived and bare a son and she called his name Tubal Cain, saying, After I had withered away have I obtained him from the Almighty God. And she conceived again and bare a daughter, and she called her name Naamah, for she said, After I had withered away have I obtained pleasure and delight.
Midrash Rabbah of Genesis
"And Lamech took two wives, Adah and Zillhah(Genesis 4:19): This what the men of the generation of the Flood would do. Each of them would take two wives, one for procreation, and the other for mere sexual pleasure. The one for procreation would sit like a widow in her lifetime[since she was used only to be made pregnant, but then had no sexual relations for any other purpose]. The one for sexual pleasure would be given a cup of bitters so that she would not become pregnant, and she would sit before her husband like a common whore."
Book of Enoch Chapter 7
1. 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. 2. And they became pregnant, and they bare great giants, whose height was three thousand ells: 3. Who consumed all the acquisitions of men. And when men could no longer sustain them, 4. the giants turned against them and devoured mankind. 5. And they began to sin against birds, and beasts, and reptiles, and fish, and to devour one another's flesh, and drink the blood. 6. Then the earth laid accusation against the lawless ones.
