Genesis 30:3-8

And she said, Behold, my maid Bilhah, go in unto her; that she may bear upon my knees, and I also may obtain 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 handmaid conceived again, and bare Jacob a second son. And Rachel said, With mighty wrestlings have I wrestled with my sister, and have prevailed: and she called his name Naphtali.