The New Testament is remarkably clear on what baptism is and what it is doing, and it is worth pausing at the outset to notice that it moves in two directions at once. Baptism is not only our confession to God and to the watching church; it is also God’s declaration over us. When a believer is baptised, God is publicly ratifying what He has done in that soul. The ordinance signs and seals the promises of the gospel to the one who receives it in faith: that their sins are washed away, that they have been united to Christ, that the Spirit has been given to them, that they belong to the new covenant people of God. This is what Paul is reaching for when he speaks of baptism alongside the washing of regeneration (Titus 3:5), and what Peter means when he calls baptism an appeal to God for a good conscience through the resurrection of Jesus Christ (1 Pet. 3:21). The water does not accomplish these things, but it visibly pledges them. God condescends to use outward and visible means to confirm inward and invisible realities, and in this the ordinance is an act of pastoral tenderness toward the weakness of our faith.
So baptism is a meeting point. God speaks to the believer through it, and the believer speaks back. Which means the two sides of that exchange belong together. And this is precisely why the question of who ought to be baptised is not as peripheral as people sometimes want to make it.
Baptism as Union with Christ
When Paul writes that we were buried with Christ by baptism into death, so that just as Christ was raised from the dead we too might walk in newness of life (Rom. 6:4), he is not describing a ceremony of admission to an outward religious community. He is describing a visible, public testimony to a spiritual reality that has already taken place in the soul. The person going down into the water and coming back up is making a declaration: I have died, my old life is finished, and everything I am now rests in the crucified and risen Christ. The sign and the thing it signifies belong together, not because the water itself does anything, but because that is what God appointed it to confess.
If baptism is a confession of union with Christ in His death and resurrection, and simultaneously God’s visible pledge of the gospel promises to the one who receives it in faith, then to administer it where no such faith exists, where repentance has neither been exercised nor professed, is to hold up a declaration where there is nothing yet to declare, and to extend a seal where there is as yet no covenant reality to confirm. The sign has been detached from its meaning on both sides of the exchange. I want to be clear that this is not said in a spirit of contempt toward brothers and sisters who disagree. The disagreement is old, and many godly and learned people stand on the other side of it. But the nature of the ordinance itself creates the pressure here. The Second London Confession simply states what the New Testament shows: the proper subject of baptism is the person who actually professes repentance toward God and faith in Christ (2LCF 29.2). That is not sectarian narrowness. That is the internal logic of what baptism is.
Circumcision and the Old Covenant Order
The standard reply, and it deserves a genuine hearing, is that baptism takes the place of circumcision, and that just as infants were circumcised under the old covenant, so they may rightly be baptised under the new. There is a surface plausibility to this. Circumcision was a genuine sign and seal of righteousness by faith (Rom. 4:11). Abraham received it as a seal upon faith he already possessed, and its deepest intention was always spiritual. That much must be granted. But the argument begins to come apart when you look carefully at the covenant order circumcision actually belonged to, rather than simply the spiritual meaning it carried.
The Abrahamic covenant was a real and glorious covenant, and it served the purposes of God in redemptive history in ways we cannot overstate. But it was not itself the covenant of grace. It was a typological covenant, distinct in its own right, which foreshadowed and pointed forward to the covenant of grace that would arrive in Christ. Within the Abrahamic covenant, and more fully within the Mosaic covenant that followed, God was doing something particular and preparatory: He was constituting a national, genealogical people through whom the Redeemer would come, and through whom the types and shadows of redemption would be displayed to the world. Circumcision was the appointed sign of membership in that typological people. It was tied to natural descent and national belonging, and it knowingly marked out a mixed body of elect and non-elect, regenerate and unregenerate together, because that was the nature of the covenant it served. Paul is plain about this: not all who are descended from Israel belong to Israel (Rom. 9:6). The outward nation and the true spiritual seed were never the same thing, and the covenant was not designed as though they were.
There is something else worth noting about circumcision. Paul tells the Galatians that every man who accepts circumcision is obligated to keep the whole law (Gal. 5:3). Circumcision was the sign of entrance into a covenant order that placed the recipient under the full weight of the Mosaic economy, with all its types and demands and shadows. It confessed a righteousness not yet accomplished, an indebtedness still outstanding. Baptism is doing something entirely different. It does not signify an obligation to establish righteousness by legal obedience. It signifies union with the One in whom all righteousness has already been accomplished and is received freely through faith. That is not a small difference. That is the difference between shadow and substance, between type and fulfilment.
The New Covenant and the End of Natural Descent
And the apostles know this. They go out of their way to dismantle confidence in natural descent as the basis of belonging to the people of God under the new order. Do not presume to say you have Abraham as your father, John the Baptist warns (Matt. 3:9). Neither circumcision nor uncircumcision counts for anything, Paul says, but a new creation (Gal. 6:15). The new covenant community is not identified by birth according to the flesh but by regeneration through the Spirit and faith in Christ. This is not incidental. It is precisely what Jeremiah said the new covenant would look like: they shall all know me, from the least to the greatest (Jer. 31:34).
This is why the new covenant is not simply the old covenant refreshed, or updated in its outward form while its essential structure remains the same. It is new in kind, because it is the covenant of grace itself, arriving in its fullness. The earlier covenants were not the covenant of grace under a different form; they were distinct covenants, typological in character, that served and pointed toward the covenant of grace. The new covenant is what they were always anticipating. And the covenant of grace, as such, has no mixed membership. Its members are those in whom the law has been written on the heart, to whom sins have been forgiven, who know the Lord not merely by external instruction but by the inward and effectual work of the Spirit. This is not to say the visible church contains no hypocrites; it plainly does, and we must be humble about the limits of our discernment. But the new covenant itself, as a covenant, is defined by those inward realities Jeremiah described, and the church’s task is to gather, as faithfully as it can, those who give credible evidence of belonging to it.
Better Covenant, Better Sign
Circumcision and baptism are therefore not parallel signs within one continuous covenantal structure. They belong to different covenants entirely, covenants with different characters, different peoples, and different appointed testimonies. The Abrahamic and Mosaic covenants both carried forward and progressively revealed the promise of redemption by farther steps, yet they remained distinct covenantal orders governed by their own particular stipulations and conditions. By contrast, the whole of the New Covenant, essentially being Christ Himself, is entirely accomplished, from first to last, by His perfect faithfulness—“since it is enacted on better promises” (Hebrews 8:6).
To insist on the connection between baptism and a credible profession of faith is not sectarianism. It is not a failure of generosity toward the broader church. It is taking seriously what God appointed the ordinance to confess and what He appointed it to pledge. Baptism carries the weight of the whole gospel: sinners dying with Christ and rising with Him to everlasting life, and God setting His seal upon that reality in the sight of the assembled church. To administer it where that confession cannot be made, or that seal has no gospel reality to confirm, is to dim the very light it was designed to shine. And that is reason enough to hold the matter with care.