Genesis 30:3-9

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.

9When Leah saw that she had ceased bearing children, she took her servant Zilpah and gave her to Jacob as a wife.