Genesis 30:3-8

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. And Rachel said, With great wrestlings have I wrestled with my sister, and I have prevailed: and she called his name Naphtali.