Genesis 30:1-5

Now when Rachel saw that she had not borne Jacob any children, she became jealous of her sister; and she said to Jacob, “Give me children, or else I am going to die.”

Then Jacob’s anger burned against Rachel, and he said, “Am I in the place of God, who has withheld from you the fruit of the womb?”

Then she said, “Here is my female slave Bilhah: have relations with her that she may give birth on my knees, so that by her I too may obtain a child.”

So she gave him her slave Bilhah as a wife, and Jacob had relations with her.

Bilhah conceived and bore Jacob a son.