Ben Tema said: Sarah said to Abraham, Write a bill of divorce, and send away this handmaid and her son from me and from Isaac my son, in this world and from the world to come. More than all the misfortunes which overtook Abraham, this matter was exceedingly evil in his eyes, as it is said, "And the thing was very grievous in Abraham's sight on account of his son" (Gen. 21:11).
Rabbi Jehudah said: In that night the Holy One, blessed be He, was revealed unto him. He said to him: Abraham! Dost thou not know that Sarah was appointed to thee for a wife from her mother's womb? She is thy companion, and the wife of thy covenant; Sarah is not called thy handmaid, but thy wife; neither is Hagar called thy wife, but thy handmaid; and all that Sarah has spoken she has uttered truthfully. Let it not be grievous in thine eyes, as it is said, "And God said unto Abraham, Let it not be grievous in thy sight" (Gen. 21:12).