Zilpah

"Then Jacob said to Laban, “Give me my wife, for my days are fulfilled, that I may go in to her.” And Laban gathered together all the men of the place and made a feast. Now it came to pass in the evening, that he took Leah his daughter and brought her to Jacob; and he went in to her. And Laban gave his maid Zilpah to his daughter Leah as a maid."

"When Leah saw that she had stopped having children, she took her servant Zilpah and gave her to Jacob as a wife. Leah’s servant Zilpah bore Jacob a son. Then Leah said, “What good fortune!” So she named him Gad."