From Calvin’s Commentary on 1 Peter 3:21
The meaning, however, is not ambiguous, that Noah, saved by water, had a sort of baptism. And this the Apostle mentions, that the likeness between him and us might appear more evident. It has already been said that the design of this clause is to shew that we ought not to be led away by wicked examples from the fear of God, and the right way of salvation, and to mix with the world. This is made evident in baptism, in which we are buried together with Christ, so that, being dead to the world, and to the flesh, we may live to God. On this account, he says that our baptism is an antitype (antitupon) to the baptism of Noah, not that Noah’s baptism was the first pattern, and ours an inferior figure, as the word is taken in the Epistle to the Hebrews, where the ceremonies of the law are said to be antitypes of heavenly things, (Hebrews 9:9,10.) Greek writers apply the same word to sacraments, so that, when they speak of the mystical bread of the holy Supper, they call it the antitype. But here there is no comparison made between the greater and the less; the Apostle only means that there is a likeness, and as they commonly say, a correspondence. Perhaps it might more properly be said to be correspondency, (antistrophon,) as Aristotle makes Dialectics to be the antistroph? of Rhetoric. But we need not labor about words, when there is an agreement about the thing itself. As Noah, then, obtained life through death, when in the ark, he was enclosed not otherwise than as it were in the grave, and when the whole world perished, he was preserved together with his small family; so at this day, the death which is set forth in baptism, is to us an entrance into life, nor can salvation be hoped for, except we be separated from the world.
“…Not the putting away of the filth of the flesh…” This was added, because it might be that the greatest part of men would profess the name of Christ; and so it is with us, almost all are introduced into the church by baptism. Thus, what he had said before would not be appropriate, that few at this day are saved by baptism, as God saved only eight by the ark. This objection Peter anticipates, when he testifies that he speaks not of the naked sign, but that the effect must also be connected with it, as though he had said, that what happened in the age of Noah would always be the case, that mankind would rush on to their own destruction, but that the Lord would in a wonderful way deliver His very small flock.
We now see what this connection means; for some one might object and say, “Our baptism is widely different from that of Noah, for it happens that most are at this day baptized.” To this he replies, that the external symbol is not sufficient, except baptism be received really and effectually: and the reality of it will be found only in a few. It hence follows that we ought carefully to see how men commonly act when we rely on examples, and that we ought not to fear though we may be few in number.
But the fanatics, such as Schuencfeldius, absurdly pervert this testimony, while they seek to take away from sacraments all their power and effect. For Peter did not mean here to teach that Christ’s institution is vain and inefficacious, but only to exclude hypocrites from the hope of salvation, who, as far as they can, deprave and corrupt baptism. Moreover, when we speak of sacraments, two things are to be considered, the sign and the thing itself. In baptism the sign is water, but the thing is the washing of the soul by the blood of Christ and the mortifying of the flesh. The institution of Christ includes these two things. Now that the sign appears often inefficacious and fruitless, this happens through the abuse of men, which does not take away the nature of the sacrament. Let us then learn not to tear away the thing signified from the sign. We must at the same time beware of another evil, such as prevails among the Papists; for as they distinguish not as they ought between the thing and the sign, they stop at the outward element, and on that fix their hope of salvation. Therefore the sight of the water takes away their thoughts from the blood of Christ and the power of the Spirit. They do not regard Christ as the only author of all the blessings therein offered to us; they transfer the glory of his death to the water, they tie the secret power of the Spirit to the visible sign.
What then ought we to do? Not to separate what has been joined together by the Lord. We ought to acknowledge in baptism a spiritual washing, we ought to embrace therein the testimony of the remission of sin and the pledge of our renovation, and yet so as to leave to Christ his own honor, and also to the Holy Spirit; so that no part of our salvation should be transferred to the sign. Doubtless when Peter, having mentioned baptism, immediately made this exception, that it is not the putting off of the filth of the flesh, he sufficiently shewed that baptism to some is only the outward act, and that the outward sign of itself avails nothing.
“…But the answer of a good conscience…” The word question, or questioning, is to be taken here for “answer,” or testimony. Now Peter briefly defines the efficacy and use of baptism, when he calls attention to conscience, and expressly requires that confidence which can sustain the sight of God and can stand before his tribunal. For in these words he teaches us that baptism in its main part is spiritual, and then that it includes the remission of sins and renovation of the old man; for how can there be a good and pure conscience until our old man is reformed, and we be renewed in the righteousness of God? and how can we answer before God, unless we rely on and are sustained by a gratuitous pardon of our sins? In short, Peter intended to set forth the effect of baptism, that no one might glory in a naked and dead sign, as hypocrites are wont to do.
But we must notice what follows, by the resurrection of Jesus Christ By these words he teaches us that we are not to cleave to the element of water, and that what is thereby typified flows from Christ alone, and is to be sought from him. Moreover, by referring to the resurrection, he has regard to the doctrine which he had taught before, that Christ was vivified by the Spirit; for the resurrection was victory over death and the completion of our salvation. We hence learn that the death of Christ is not excluded, but is included in his resurrection. We then cannot otherwise derive benefit from baptism, than by having all our thoughts fixed on the death and the resurrection of Christ.