Genesis 30:3-7

And she said, Behold my maid Bilhah, go in unto her; and she shall bear upon my knees, that I may also have children by her.

And she gave him Bilhah her handmaid to wife: and Jacob went in unto her.

And Bilhah conceived, and bare Jacob a son.

And Rachel said, God hath judged me, and hath also heard my voice, and hath given me a son: therefore called she his name Dan.

And Bilhah Rachel’s maid conceived again, and bare Jacob a second son.