Genesis 17:12–22 — The Eighth Day, Sarah's Name Changed, and Isaac Distinguished from Ishmael

The Eighth Day — Death and Something New

Genesis 17:12 specifies: he that is eight days old shall be circumcised among you, every man-child in your generations. The eighth day is not incidental. Seven completes a week; eight begins what follows. The eighth day is the day after the full cycle of the old creation — it points to resurrection, to something new beyond the present order. The Lord Jesus rose from the dead on the first day of the new week, which is simultaneously the eighth day after the Sabbath of the old covenant. Circumcision on the eighth day placed the mark of death on the first man precisely in view of what was coming beyond death.

This connection between the eighth day and resurrection is developed in Colossians 2:11–12, where we learn that we have been circumcised with the circumcision of Christ — not with hands — the putting off of the body of flesh, buried with Him in baptism, risen with Him through faith in the working of God who raised Him from the dead. The circumcision of Christ is identified with His death and our co-death with Him, and it issues in resurrection. So the eighth day of circumcision was always pointing forward to Christ in death and resurrection as the one event that gives the rite its real meaning.

Even the Lord Jesus was circumcised on the eighth day. Luke 2:21 records it, and in a remarkable way: and when eight days were accomplished for the circumcising of the child, his name was called Jesus. The verse is almost structured to say that the main point of that occasion was the name, not the rite — as if to declare, the one who underwent the mark of death is Jehovah the Saviour. He identified Himself with the circumcised — with those upon whom the sentence of death had been inscribed. And He was one of the seed of Abraham, but the great unique seed, the administrator of all God's purposes in resurrection.

The Soul Cut Off — What Breaking the Covenant Means

Verse 14: the uncircumcised man-child, that soul shall be cut off from his people. He hath broken my covenant. Moses provides the interpretive key. When he was on his way back to Egypt to be the deliverer of God's people, the angel met him in the way to destroy him. Zipporah understood immediately and circumcised her son — she called Moses a bloody man, for she had no liking for the rite. But the point is plain: the one appointed to deliver the circumcised people could not himself have an uncircumcised house. He had failed in this, and his life was in danger until it was set right.

The principle is that the sentence of death — God's judgment on the first man, the cutting off of confidence in the flesh — must mark the household of the man of God. To hold back on this for one's own house, while submitting to it personally, was precisely the failure the Lord would not pass over in Moses. Abraham's obedience extended to everyone under his authority without exception: born in the house, bought with money, male of every age. No one had a vote on the matter; no one was consulted; it was done on the selfsame day.

Sarah's Name — From My Princess to Princess

Verse 15: as for Sarai thy wife, thou shalt not call her name Sarai, but Sarah shall be her name. Sarai means my princess — a name from nature, Abraham's princess, the princess of his household as seen by those who knew her. Sarah means simply princess — the princess, in connection with God's purpose. The my is dropped. What was hers by natural relationship became hers by divine appointment. She was to be the mother of the son who is the heir according to promise, the great type of the Lord Jesus. A name change was required, because the old name marked what she was in nature; the new name marked what God was making her.

This principle of name change in connection with God's purpose appears throughout Scripture. Abram to Abraham, Jacob to Israel, Simon to Peter. The new name expresses the divine purpose for the person. And in Revelation 2:17, the overcomer receives a new name which no man knows but he that receives it — deeply personal, not absorbed into a formless infinity, but a distinct and individual relationship between that soul and the Lord.

Abraham's Laughter — Joy, Not Unbelief

Verse 17: then Abraham fell on his face and laughed, and said in his heart, Shall a child be born unto him that is a hundred years old, and shall Sarah that is ninety years old bear? Abraham was not rebuked for this laugh. When Sarah laughed at the same news in chapter 18, she was directly rebuked — nay, but thou didst laugh. Why the difference?

Abraham believed. His faith was accounted to him for righteousness in chapter 15, long before either circumcision or this moment. His laugh was the laugh of Psalm 126: when the Lord turned again the captivity of Zion, we were like them that dreamed, then was our mouth filled with laughter. It was the laughter of a man who lays hold of something that is impossible in nature but certain in God. He acknowledged the impossibility — shall a child be born unto him that is a hundred years old — but he believed it, and joy broke out. Sarah's laugh was different in character: it was a laugh that denied the possibility. Abraham's said, this is beyond nature, and God will do it. Sarah's said, this cannot happen.

God confirmed this reading by naming the son Isaac — laughter. Every time Abraham called his son's name, he was calling out the memory of that moment of pure joy. God the Father said of the Lord Jesus, this is my beloved Son, in whom I have found all my delight. The delight of the Father in the only begotten Son is reflected even in Isaac's name — pure, unadulterated joy in the unique heir.

Thou shalt call his name Isaac — laughter. God put his stamp of approval on that laughter of faith. — Genesis 17:19

O That Ishmael Might Live Before Thee — Promises Versus

Covenant

Verse 18: Abraham said, O that Ishmael might live before thee. He knew Ishmael was about to be displaced by the coming heir. He had been a father to Ishmael for thirteen years, and he loved him. His prayer was not for Ishmael to be the heir — he believed what God had said — but that Ishmael might have some portion too.

God's answer is important for another reason: it sharpens the distinction between promise and covenant. There are blessings and I wills spoken over Ishmael: I will make him fruitful, I will multiply him exceedingly, twelve princes shall he beget, I will make him a great nation. These are promises. But verse 21: but my covenant will I establish with Isaac. The covenant is not extended to Ishmael. The promises for Ishmael are real, and they have been fulfilled in history. But the covenant — the one-sided unconditional divine undertaking through which God will bless all the nations and make good every word He has spoken to Abraham — centres in Isaac, and in the great seed of Abraham to whom Isaac points.

As for Ishmael, I have heard thee — that is the meaning of Ishmael's name, God hears. And God did hear. But the covenant, with its I wills and its everlasting character, was with Isaac. Not all divine blessings are covenantal blessings. Every promise of God is not necessarily part of the Abrahamic covenant. But those that are covenanted rest on one party only — El Shaddai — and will be made good in every last detail.

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