211 Yahweh visited Sarah as he had said, and Yahweh did to Sarah as he had spoken. 2 Sarah conceived, and bore Abraham a son in his old age, at the set time of which God had spoken to him. 3 Abraham called his son who was born to him, whom Sarah bore to him, Isaac. [1] 4 Abraham circumcised his son, Isaac, when he was eight days old, as God had commanded him. 5 Abraham was one hundred years old when his son, Isaac, was born to him. 6 Sarah said, “God has made me laugh. Everyone who hears will laugh with me.” 7 She said, “Who would have said to Abraham, that Sarah would nurse children? For I have borne him a son in his old age.”
Matthew Henry's Commentary on Genesis 21:1-7
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.