211 God visited Sarah exactly as he said he would; God did to Sarah what he promised: 2 Sarah became pregnant and gave Abraham a son in his old age, and at the very time God had set. 3 Abraham named him Isaac. 4 When his son was eight days old, Abraham circumcised him just as God had commanded. 5 Abraham was a hundred years old when his son Isaac was born. 6 Sarah said, God has blessed me with laughter and all who get the news will laugh with me! 7 She also said, Whoever would have suggested to Abraham that Sarah would one day nurse a baby! Yet here I am! I've given the old man a son!
8 The baby grew and was weaned. Abraham threw a big party on the day Isaac was weaned.
9 One day Sarah saw the son that Hagar the Egyptian had borne to Abraham, poking fun at her son Isaac. 10 She told Abraham, "Get rid of this slave woman and her son. No child of this slave is going to share inheritance with my son Isaac!" 11 The matter gave great pain to Abraham - after all, Ishmael was his son. 12 But God spoke to Abraham, "Don't feel badly about the boy and your maid. Do whatever Sarah tells you. Your descendants will come through Isaac. 13 Regarding your maid's son, be assured that I'll also develop a great nation from him - he's 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.