John Gills Exposition of the Bible Commentary - Genesis 21:1
And the Lord visited Sarah as he had said ,.... To Abraham, Genesis 17:16 ; in a way of mercy and kindness, by fulfilling his promise, giving strength to conceive and bear a child; see 1 Samuel 2:21 , and the Lord did unto Sarah as he had spoken ; which intends the same thing in different words; and the repetition is made to cause attention to God's fulfilment of his promise, who is always faithful to his word, even in things very difficult and seemingly impossible, as in the present... read more
Matthew Henry's Complete Commentary - Genesis 21:1-8
Few under the Old Testament were brought into the world with such expectation as Isaac was, not for the sake of any great person eminence at which he was to arrive, but because he was to be, in this very thing, a type of Christ, that seed which the holy God had so long promised and holy men so long expected. In this account of the first days of Isaac we may observe, I. The fulfilling of God's promise in the conception and birth of Isaac, Gen. 21:1, 2. Note, God's providences look best and... read more