211 The Lord kept his word and did for Sarah exactly what he had promised. 2 She became pregnant, and she gave birth to a son for Abraham in his old age. This happened at just the time God had said it would. 3 And Abraham named their son Isaac. 4 Eight days after Isaac was born, Abraham circumcised him as God had commanded. 5 Abraham was 100Â years old when Isaac was born. 6 And Sarah declared, "God has brought me laughter. All who hear about this will laugh with me. 7 Who would have said to Abraham that Sarah would nurse a baby? Yet I have given Abraham a son in his old age!"
8 When Isaac grew up and was about to be weaned, Abraham prepared a huge feast to celebrate the occasion.
9 But Sarah saw Ishmael-the son of Abraham and her Egyptian servant Hagar-making fun of her son, Isaac. 10 So she turned to Abraham and demanded, "Get rid of that slave woman and her son. He is not going to share the inheritance with my son, Isaac. I won't have it!" 11 This upset Abraham very much because Ishmael was his son. 12 But God told Abraham, "Do not be upset over the boy and your servant. Do whatever Sarah tells you, for Isaac is the son through whom your descendants will be counted. 13 But I will also make a nation of the descendants of Hagar's son because he is your son, too."
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.