Genesis 30:3-8

3Then she said, “Here is my servant Bilhah; go in to her, so that she may give birth on my behalf, that even I may have children through her.” 4So she gave him her servant Bilhah as a wife, and Jacob went in to her. 5And Bilhah conceived and bore Jacob a son. 6Then Rachel said, “God has judged me, and has also heard my voice and given me a son.” Therefore she called his name Dan. 7Rachel’s servant Bilhah conceived again and bore Jacob a second son. 8Then Rachel said, “With mighty wrestlings I have wrestled with my sister and have prevailed.” So she called his name Naphtali.