Genesis 21:1-7

"And Jehovah visited Sarah, as he had said, and Jehovah did unto Sarah as he had spoken. And Sarah conceived, and bare Abraham's son in his old age, at the set time of which God had spoken to him. And Abraham called the name of his son that was born unto him, whom Sarah bare to him, Isaac. And Abraham circumcised his son Isaac when he was eight days old, as God had commanded him. And Abraham was a hundred years old, when his son Isaac was born unto him. And Sarah said, God hath made me to laugh; every one that heareth will laugh with me. And she said, Who would have said unto Abraham, that Sarah should give children suck? for I have borne him a son in his old age."

Genesis 21:1 and Genesis 21:2 stress the fact that God is a God who keeps and fulfills His promises. Note the recurrence of "as he had said ... as he had spoken ... at the set time of which God had spoken." For a full quarter of a century, Abraham and Sarah had awaited this fulfillment, and then it was done."

"Isaac ..." means laughter, memorializing Sarah's laughing incredulity at the time of God's promise, and also, in a wider context, appropriately referring to the joy that would come to all people through that "Seed singular," who in the fullness of time would be delivered through the posterity of the same Isaac. It is foolish to seek variant sources on such details as whether the father or the mother bestowed the name on a new child, because in a number of instances, God Himself gave the name, as was true both of Isaac (Genesis 17:19), and of Ishmael (Genesis 16:11).

"Circumcised ... when he was eight days old ..." This continued ever afterward as the invariable custom of the Jews; but the Arabians who descended through Ishmael observe the rite at the beginning of the 13th year, as it was initiated in the instance of Ishmael. Christ also was circumcised the eighth day; and thus Christians are "in Christ" circumcised with the "circumcision not made with hands" (Colossians 2:11,12). For the old Israel, circumcision was not the covenant, but the sign of the covenant; but for Christians, circumcision (in the spiritual sense) is the union with Christ by means of being baptized "into him."

"Abraham was a hundred years old ..." Sarah was ninety at the same time when Isaac was born; supernatural gifts were conveyed to both of them in order to make possible the birth of Isaac, "the child of promise" (Galatians 4:28).

"That Sarah should give children suck ..." Sarah's speaking of Isaac here as "children" is significant. Willis was doubtless correct in the observation that, "Passages such as this show that a man with one child is suitable to serve as an elder, if his spiritual qualities are on a high godly plane (1 Timothy 3:4; Titus 1:6)."[1]

All of the happiness that should have come to Abraham and Sarah with the birth of this long-awaited son, however, did not come. The terrible evils of polygamy, and the tangled affairs of their domestic life, resulted almost at once in jealousy, strife, enmity, and division. The climax came on the occasion of the feast given to celebrate the weaning of Isaac.