When Sarah lost all hope of having her own child, she gave Abraham her servant Hagar, so that Abraham would have a son through her.

Sarah intended to recognize Hagar's son Ishmael as her own son, and to give him the special status that ancient society reserved for the oldest son. She intended for him to be Abraham’s successor, the one who would continue his lineage.

For example, what right did Sarah have to give her maidservant to Abraham so that she would have a child for her? What were the legal relationships between her and Hagar? What status did Ishmael, the son born to Hagar, have?

Hagar exploited the fact that she gave birth to Abraham’s firstborn son to mock and humiliate Sarah. She felt that the pregnancy had turned the hierarchy of Abraham’s household upside down. Hagar was now in the superior position, able to mock Sarah for her barrenness.