In the Book of Genesis, Zilpah (זִלְפָּה "meaning uncertain," Standard Hebrew Zilpa, Tiberian Hebrew Zilpâ) was Leah's handmaid, whom Leah gave to Jacob "to wife" to bear him children (Genesis 30:9). Zilpah gave birth to two sons, whom Leah claimed as her own and named Gad and Asher (Genesis 30:10-13).
Zilpah is given to Leah as a handmaid by Leah's father, Laban, upon Leah's marriage to Jacob (see Genesis 29:24, 46:18). According to the early rabbinical commentary Pirke De-Rabbi Eliezer, Zilpah and Bilhah, the handmaids of Leah and Rachel, respectively, were actually younger daughters of Laban.
Zilpah also figures in the competition between Jacob's wives to bear him sons. Leah stops conceiving after the birth of her fourth son, at which point Rachel, who had not yet borne children, offers her handmaid, Bilhah, "to wife" to Jacob so that she can have children through her. When Bilhah conceives two sons, Leah takes up the same idea and presents Zilpah "to wife" to Jacob. Leah names the two sons of Zilpah and is directly involved in their upbringing.
According to Rashi, an 11th-century commentator, Zilpah was younger than Bilhah, and Laban's decision to give her to Leah was part of the deception he used to trick Jacob into marrying Leah, who was older than Rachel. The morning after the wedding, Laban explained to Jacob, "This is not done in our place, to give the younger before the older" (Genesis 29:26). But at night, to mask the deception, Laban gave the veiled bride the younger of the handmaids, so Jacob would think that he was really marrying Rachel, the younger of the sisters.