The Book of the Cave of Treasures 50

1And when Isaac was forty years old, Eliezer, a son of the house of Abraham, went down and brought Rabka (Rebecca) from the east, and Isaac took her to wife. And when Abraham died Isaac buried him by the side of Sara.
2And when Isaac was sixty years old Rebecca became with child of Esau and Jacob. And being sorely afflicted, she went to Melchisedek, and he prayed over her and said unto her, ‘‘ Two nations are in thy womb, and two peoples shall be removed from thy loins, that is to say, shall go forth from thy womb. One nation shall be stronger than the other, and the elder shall be in subjection to the younger, that is to say, Esau shall be in subjection to Jacob.”