Simple answer to this post’s title: Because circumcision is the sign of the covenant for the offspring of Abraham.
Now here might be a head-scratcher, because that line sounds quite paedobaptist. Indeed at the root of a good deal of paedobaptism is the idea that an overarching covenant of grace exists, under which all the biblical covenants fall. Therefore the New Covenant (somehow despite Jeremiah 31 and Hebrews 8, which tell us it is completely different) is basically the same as the Old. According to such Covenant Theology, there is not much core difference between Israel and the Church. Therefore as they circumcised their infant males, showing they belong to the covenant community; so we should baptize our infants showing they belong to our covenant community.
By the way, side note wondering: if there is such a direct link between circumcision and baptism, why do we not limit baptism only to our males?
Well that answer is precisely that there is a difference. On the one hand, unlike some of my dispensational brethren (even if they do have cool charts—sorry Dave Miller), I do not think the Bible teaches the church is wholly new. All the reasons why belong in another blog post (or several), but suffice it to say for my purpose here I think there is a direct connection and a continual line from the faithful ekklesia (to borrow the LXX usage) within the Old Testament nation of Israel to the New Testament ekklesia—a redeemed people of both Jews and Gentiles.
On the other hand, the Bible teaches that the church is in some ways functionally and structurally different than national Israel. And part of that has to do with the New Covenant. After all, what is the purpose of the New Covenant to which the church clearly belongs (Luke 22:20, 1 Corinthians 11:25, 2 Corinthians 3:4ff)? According to Jeremiah 31:31ff, it is to replace the covenant with Moses. It will not be like the one God made with their fathers when he led them out of Egypt, a covenant of laws written on stone, a covenant which they broke though God was faithful to them.
Instead, with the New Covenant, God’s law will be written on the hearts of his people, they will truly be his and he shall be their God, they will all know the Lord, and their sins will be forever forgiven.
And here we find a defining shift in the covenant people.
On the one hand, these people are still of the offspring of Abraham—they belong to the house of Israel and house of Judah. On the other hand, they are a particular group within the offspring of Abraham. Moses hinted at this a couple of times in Deuteronomy. Jeremiah spoke of it in 9:25-26. These are people who are circumcised of the heart.
Certainly these people, a faithful remnant, existed among the nation. But the covenant with Moses was not exclusive to them. God gave all facets of the Law to the nation as the whole. Even if a person did not actually believe God’s word, there existed a civil expectation to keep the Law or face the consequences. But since these laws were written on stone and not on the heart, they failed to bring righteousness and only magnified the unrighteousness of the faithless.
In the nation of Israel it was possible for a person to belong to the covenant people yet not “know the Lord.” Under the New Covenant this is no longer possible.
In both cases, the covenant people remain the offspring of Abraham. In Genesis and indeed the entire biblical story we see a peculiar reality about God’s promise to Abraham to build a great people out of his seed, give them a land as their inheritance, and bless the earth. The reality is it never had to do with all of Abraham’s physical offspring.
Ishmael was the firstborn, but he was not the child of promise. Abraham had several more children after Sarah died. Not much is said about them. The covenant and promises passed to Isaac, the child of promise. Even then all of his offspring did not participate. “Jacob I loved, Esau I hated,” God said. The covenant and promises passed to Jacob and his sons while Esau stood rejected. Generations later, God even spoke to the majority of the nation—think of the prophecy through Hosea. “You are not my people.” Jesus argued with men who prided themselves on being the children of Abraham. Jesus told them, “You are of your father, the devil.”
All of these are the physical offspring of Abraham, but a clear distinction exists. Some are offspring included in the promise, and others are offspring excluded.
Now how does this apply to the life of the church as the New Covenant community? In the New, the covenant people are still the offspring of Abraham but we find again this is not about a physical linage. Aside from those remarks by Jesus to a group of Jews in John 8, Paul wrote in Romans 2:28-29, “No one is a Jew who is merely one outwardly, nor is circumcision outward and physical. But a Jew is one inwardly and circumcision is a matter of the heart, by the Spirit.”
To be counted among the offspring of Abraham, circumcision still matters, but not a circumcision of the flesh. At stake is the condition of the heart, the very truth the Old Testament pointed to when there existed a mixed covenant community of believer and unbeliever.
Paul further clarified the identity of Abraham’s offspring to the churches of Galatia, churches in a predominately Gentile region who began to let go of the true Gospel for a false one that required the circumcision of the flesh for salvation. Paul made several points: 1) Through Christ and faith in him the blessing of Abraham came to the Gentiles (3:14); 2) God’s promises to Abraham, while beneficial to the nation that came as the offspring of Abraham, were not truly focused on a nation. They were focused on an individual—that being Christ. Jesus was ultimately the child of promise to whom the covenant belonged (3:16-17); and 3) on account of this, we who were “baptized into Christ have put on Christ” thus no spiritual distinction nor distinction of promise remains between Jew or Greek, slave or free, male or female, etc., for, “If you are Christ’s then you are Abraham’s offspring, heirs according to the promise” (3:27-29).
This very thing Paul also described in Romans 9-11. God’s promises to Israel never failed, though many Israelites were rejected, because God’s word to Abraham was never about the flesh but the “children of promise” who “are counted as offspring.” Again, a promise that in Christ extends to Jew and Gentile—whoever will believe. And though Jews should belong as “natural” branches, God grafts believing Gentiles into the olive tree of Israel, Abraham’s offspring, in place of disbelieving Jews.
With this further clarification of who belongs to Abraham’s children, and the reality that it is ultimately by promise and faith in Christ we see the shape of the New Covenant—in that all who are under the covenant will know the Lord and their sins will be forgiven.
This brings us to the covenant sign. In Genesis 17, God told Abraham that he and his children were to circumcise all the males born to them. This removal of flesh became the sign and seal of God’s promises. As Moses, Jeremiah, and Paul recorded—removing the dead flesh of a rebellious heart was the real issue. Then in Colossians 2:11-14 Paul wrote this:
In [Christ] also you were circumcised with a circumcision made without hands, by putting off the body of the flesh, by the circumcision of Christ, having been buried with him in baptism, in which you were also raised with him through faith in the powerful working of God, who raised him from the dead. And you who were dead in your trespasses and the uncircumcision of your flesh, God made alive together with him, having forgiven us all our trespasses, by canceling the record of debt that stood against us with its legal demands. This he set aside, nailing it to the cross.
In Paul’s words we find New Covenant language in the forgiveness of all our trespasses. Several verses later, Paul continued with the theme of the old self being dead and the new self being alive, and he repeated the idea from Galatians 3: “Here there is not Greek and Jew, circumcised and uncircumcised, barbarian, Scythian, slave, free; but Christ is all and in all” (3:11).
We see that in belonging to Christ, therefore belonging to Abraham’s linage by virtue of the offspring, we are also circumcised. It is through the circumcision of Christ. He fulfilled perfectly the role of Abraham’s offspring. To him belong the land (the world), through him comes the nation (God’s people from every tribe, tongue, and language), and through him comes the blessing for the world (salvation and restoration). Furthermore, he achieved this by perfectly embodying the righteousness described in the Law. Jesus was circumcised on the 8th day, and by virtue of belonging to him we were circumcised on that same day.
And with the circumcision of Christ applied to us, we also see the circumcision of the heart. The body of flesh (of sin) has been put off and we are made alive. The mark of the New Covenant, then, is a sign of this whole-body circumcision. We are baptized. By going into the waters, we show the sinful nature of our old self has been buried with Christ. It is circumcised, stripped off, and removed. By coming out of the waters, we show we have risen to new life in Christ. We are cleansed and forgiven.
Undoubtedly, then, in the New Covenant declarations, in the true definition of Abraham’s offspring, and in the meaning of baptism, baptism is in no way applicable to those who do not belong to Christ (and thus Abraham) by faith. The covenant community consists solely of those who have turned from sin and turned to Christ. We hope one day our children will belong through the work of the Gospel, but it is wholly inappropriate to baptize them as if they belong before they have truly made a commitment to follow Christ in faith.
I am a credobaptist and cannot be a paedobaptist because circumcision is the sign of the covenant for the offspring of Abraham.