Matthew Henry Commentary Genesis 21:9-13

"And Sarah saw the son of Hagar the Egyptian, whom she had borne unto Abraham, mocking. Wherefore she said unto Abraham, Cast out this handmaid and her son. For the son of this handmaid shall not be heir with my son, even with Isaac. And the thing was very grievous in Abraham`s sight on account of his son. And God said unto Abraham, Let it not be grievous in thy sight because of the lad, and because of thy handmaid. In all that Sarah saith unto thee, hearken unto her voice. For in Isaac shall thy seed be called. And also of the son of the handmaid will I make a nation, because he is thy seed." — Genesis 21:9-13 (ASV)

Let us not overlook how this family matter instructs us not to rest in outward privileges or in our own deeds. And let us seek the blessings of the new covenant by faith in its Divine Surety. Ishmael's conduct was persecution, being done in profane contempt of the covenant and promise, and with malice against Isaac.

God takes notice of what children say and do in their play, and will call them to account if they say or do wrong, even if their parents do not. Mocking is a great sin, and very provoking to God. And the children of promise must expect to be mocked.

Abraham was grieved that Ishmael misbehaved and that Sarah demanded such a severe punishment. But God showed him that Isaac must be the father of the promised Seed, and that therefore Ishmael should be sent away, lest he corrupt Isaac's behavior or try to usurp his rights. The covenant seed of Abraham must be a people by themselves, not mingled with those who were out of covenant. Sarah had little thought of this, but God turned her words to His good purpose.