211 The Lord dealt with Sarah as he had said, and the Lord did for Sarah as he had promised. 2 Sarah conceived and bore Abraham a son in his old age, at the time of which God had spoken to him. 3 Abraham gave the name Isaac to his son whom Sarah bore him. 4 And Abraham circumcised his son Isaac when he was eight days old, as God had commanded him. 5 Abraham was a hundred years old when his son Isaac was born to him. 6 Now Sarah said, "God has brought laughter for me; everyone who hears will laugh with me." 7 And she said, "Who would ever have said to Abraham that Sarah would nurse children? Yet I have borne him a son in his old age."
8 The child grew, and was weaned; and Abraham made a great feast on the day that Isaac was weaned.
9 But Sarah saw the son of Hagar the Egyptian, whom she had borne to Abraham, playing with her son Isaac. 10 So she said to Abraham, "Cast out this slave woman with her son; for the son of this slave woman shall not inherit along with my son Isaac." 11 The matter was very distressing to Abraham on account of his son. 12 But God said to Abraham, "Do not be distressed because of the boy and because of your slave woman; whatever Sarah says to you, do as she tells you, for it is through Isaac that offspring shall be named for you. 13 As for the son of the slave woman, I will make a nation of him also, because he is your offspring."
Matthew Henry's Commentary on Genesis 21:1-13
Commentary on Genesis 21:1-8
(Read Genesis 21:1-8)
Few under the Old Testament were brought into the world with such expectations as Isaac. He was in this a type of Christ, that Seed which the holy God so long promised, and holy men so long expected. He was born according to the promise, at the set time of which God had spoken. God's promised mercies will certainly come at the time which He sets, and that is the best time. Isaac means "laughter," and there was good reason for the name, Psalm 22:9,10; Hosea 11:1,2.
Commentary on Genesis 21:9-13
(Read Genesis 21:9-13)
Let us not overlook the manner in which this family matter instructs us not to rest in outward privileges, or in our own doings. 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 reckon with them, if they say or do amiss, though 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 should misbehave, and Sarah demand so severe a punishment. But God showed him that Isaac must be the father of the promised Seed; therefore, send Ishmael away, lest he corrupt the manners, or try to take the rights of Isaac. The covenant seed of Abraham must be a people by themselves, not mingled with those who were out of covenant: Sarah little thought of this; but God turned aright what she said.