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!"
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.