Genesis 30:3-8

She said, “Here is my maid Bilhah, go in to her that she may bear on my knees, that through her I too may have children.” So she gave him her maid Bilhah as a wife, and Jacob went in to her. Bilhah conceived and bore Jacob a son. Then Rachel said, “God has vindicated me, and has indeed heard my voice and has given me a son.” Therefore she named him Dan. Rachel’s maid Bilhah conceived again and bore Jacob a second son. So Rachel said, “With mighty wrestlings I have wrestled with my sister, and I have indeed prevailed.” And she named him Naphtali.