(3) Abraham called the name of his son.—Attention has been called to the fact that we have here two things contrary to subsequent usage: for, first, the father names the child, and not the mother; and, secondly, he names him at his birth, instead of waiting until his circumcision. It might be enough to answer that the child was really named by God (Genesis 17:19), and that Abraham only acknowledges that the son born was the promised Isaac; but really, as we have seen before, there was as yet no settled rule as to either of these points.

Isaac.—This name not only recorded the fact of the laughter of the father (Genesis 17:17) and of the mother (Genesis 18:12), but was a standing memorial that Isaac’s birth was contrary to nature, and one of which the promise was provocative of ridicule in the sight even of his parents.

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, ch. 17:17; 18:13. When the Sun of comfort is risen upon the soul, it is good to remember how welcome the dawning of the day was. When Sarah received the promise, she laughed with distrust and doubt. When God gives us the mercies we began to despair of, we ought to remember with sorrow and shame our sinful distrust of his power and promise, when we were in pursuit of them. This mercy filled Sarah with joy and wonder. God's favours to his covenant people are such as surpass their own and others' thoughts and expectations: who could imagine that he should do so much for those that deserve so little, nay, for those that deserve so ill? Who would have said that God should send his Son to die for us, his Spirit to make us holy, his angels to attend us? Who would have said that such great sins should be pardoned, such mean services accepted, and such worthless worms taken into covenant? A short account of Isaac's infancy is given. God's blessing upon the nursing of children, and the preservation of them through the perils of the infant age, are to be acknowledged as signal instances of the care and tenderness of the Divine providence. See Ps 22:9,10; Ho 11:1,2.Isaac is born according to promise, and grows to be weaned. "The Lord had visited Sarah." It is possible that this event may have occurred before the patriarchal pair arrived in Gerar. To visit, is to draw near to a person for the purpose of either chastising or conferring a favor. The Lord had been faithful to his gracious promise to Sarah. "He did as he had spoken." The object of the visit was accomplished. In due time she bears a son, whom Abraham, in accordance with the divine command, calls Isaac, and circumcises on the eighth day. Abraham was now a hundred years old, and therefore Isaac was born thirty years after the call. Sarah expressed her grateful wonder in two somewhat poetic strains. The first, consisting of two sentences, turns on the word laugh. This is no longer the laugh of delight mingled with doubt, but that of wonder and joy at the power of the Lord overcoming the impotence of the aged mother. The second strain of three sentences turns upon the object of this admiring joy. The event that nobody ever expected to hear announced to Abraham, has nevertheless taken place; "for I have borne him a son in his old age." The time of weaning, the second step of the child to individual existence, at length arrives, and the household of Abraham make merry, as was wont, on the festive occasion. The infant was usually weaned in the second or third year 1 Samuel 1:22-24; 2 Chronicles 31:16. The child seems to have remained for the first five years under the special care of the mother Leviticus 27:6. The son then came under the management of the father.3, 4. Abraham called the name of his son … Isaac … and circumcised—God was acknowledged in the name which, by divine command, was given for a memorial (compare Ge 17:19), and also in the dedication of the child by administering the seal of the covenant (compare Ge 17:10-12). No text from Poole on this verse.

And Abraham called the name of his son that was borne unto him, whom Sarah bare to him, Isaac. Which is the name he was directed to give him, Genesis 17:19; and he remembers the order, and is obedient to it; the reason of which name, which signifies laughter, was on account of his laughing for joy at the promise made him, as well as there might be afterwards a further reason for it, from Sarah's laughing through distrust; and it might presignify the joy and laughter that would be expressed by others at his birth; and perhaps also that he would be the object of the laughter and derision of his brother; such a number of events agreeing with his name. And Abraham called the name of his son that was born unto him, whom Sarah bare to him, Isaac.