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!
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.