Acts 2:38

For whereas in the Gospels, and in the epistles of the apostles, the name of Christ is alleged for the remission of sins; it is not in such a way as that the Son alone, without the Father, or against the Father, can be of advantage to anybody; but that it might be shown to the Jews, who boasted as to their having the Father, that the Father would profit them nothing, unless they believed on the Son whom He had sent. For they who know God the Father the Creator, ought also to know Christ the Son, lest they should flatter and applaud themselves about the Father alone, without the acknowledgment of His Son, who also said, "No man cometh to the Father but by me." But He, the same, sets forth, that it is the knowledge of the two which saves, when He says, "And this is life eternal, that they might know Thee, the only true God, and Jesus Christ, whom thou hast sent." Since, therefore, from the preaching and testimony of Christ Himself, the Father who sent must be first known, then afterwards Christ, who was sent, and there cannot be a hope of salvation except by knowing the two together; how, when God the Father is not known, nay, is even blasphemed, can they who among the heretics are said to be baptized in the name of Christ, be judged to have obtained the remission of sins? For the case of the Jews under the apostles was one, but the condition of the Gentiles is another. The former, because they had already gained the most ancient baptism of the law and Moses, were to be baptized also in the name of Jesus Christ, in conformity with what Peter tells them in the Acts of the Apostles, saying, "Repent, and be baptized every one of you in the name of the Lord Jesus Christ, for the remission of sins, and ye shall receive the gift of the Holy Ghost. For this promise is unto you, and to your children, and to all that are afar off, even as many as the Lord our God shall call." Peter makes mention of Jesus Christ, not as though the Father should be omitted, but that the Son also might be joined to the Father.

and be baptized, each one of you, in the name of Jesus Christ: Saving holy Baptism suffices for our cleansing of sin, and erases the stain of previous falls.

Here again Peter, though the question is put to all, is the man to answer. "Repent," says he, "and be baptized every one of you, in the name of Jesus Christ." He does not yet say, Believe, but, "Be baptized every one of you." For this they received in baptism. Then he speaks of the gain; "For the remission of sins, and ye shall receive the gift of the Holy Ghost." If you are to receive a gift, if baptism conveys remission, why delay?

What had been said was not enough. For those sayings indeed were sufficient to bring them to faith; but these are to show what things the believer behooves to do. And he said not, In the Cross, but, "In the name of Jesus Christ let every one of you be baptized." And he does not put them continually in mind of the Cross, that he may not seem to reproach them, but he says simply, "Repent: and why? That we may be punished? No: "And let each of you be baptized in the name of Jesus Christ, for the remission of sins." And yet quite other is the law; of this world's tribunals: but in the case of the Gospel proclamation; when the delinquent has confessed, then is he saved! Observe how Peter does not instantly hurry over this, but he specifies also the conditions, and adds, "Ye shall receive the gift of the Holy Ghost;" an assertion accredited by the fact, that the Apostles themselves had received that gift.

As the mouth of all the apostles put forward, Peter says, Repent and be baptized, not believe, but, "Be baptized." For this is the foundation of those who believe in Christ. Therefore he requires this first, and after this he brings the end toward the foundation, saying "the gift of the Holy Spirit," as revealed through this faith.

Hence Peter, when he saw some affrighted by consideration of their evil deeds, admonished them, saying, Repent, and be baptized every one of you. For, being about to speak of baptism, he spoke first of the lamentations of penitence; that they should first bathe themselves in the water of their own affliction, and afterwards wash themselves in the sacrament of baptism. With what conscience, then, can those who neglect to weep for their past misdeeds live secure of pardon, when the chief pastor of the Church himself believed that penitence must be added even to this Sacrament which chiefly extinguishes sins?

And you will receive the gift of the Holy Spirit. For the promise is to you and to your children, as the Lord says through the prophet: I will pour out My Spirit on all flesh, and your sons and your daughters shall prophesy (Joel II). And what he added: And to all who are afar off, as many as the Lord our God shall call, refers to that final testimony placed from the prophet, that everyone who calls upon the name of the Lord shall be saved (Ibid.). This particularly pertains to the calling of the Gentiles, who were far removed from the fellowship of the sons of Israel in both kinship and merit, and yet were to be saved by invoking the name of the Lord according to the prophet's promise.

"Repent," he says, "and let each one of you be baptized." Speaking of baptism, he first mentioned the laments of repentance, so that, following the custom of the Church, they might first immerse themselves in the water of their affliction, and afterward be washed in the sacrament of baptism.

Although the question was posed to all the apostles, "Peter" again answers — since the apostles themselves preferred his mouth — and says: "Repent, and let each of you be baptized in the name of Jesus Christ." These words do not contradict the following words of the Gospel: "Baptizing them in the name of the Father and of the Son and of the Holy Spirit" (Matt. 28:19), because the Church confesses the Holy Trinity as undivided, so that, by virtue of the unity of the three hypostases in essence, the one baptized in the name of Christ is baptized into the Trinity, since the Father and the Son and the Holy Spirit are undivided in essence. If the name of the Father were not God, and the name of the Son were not God, and the name of the Holy Spirit were not God, then one would have to say "in the name of God Jesus Christ," or even simply — only "in the Son." But Peter says in the "name of Jesus Christ," knowing that the name of Jesus is God, just as the name of the Father and the name of the Holy Spirit are also God.

Since the power that restores us is the power of the whole Trinity, which holy mother Church believes in the mind, confesses in word, and professes in sign, under the distinction and property, order and natural origin of the three persons: hence it is that for the expression of these things in the Sacrament which is the first of all Sacraments, and in which this power operates firstly and principally, there ought to be an expression of the Trinity in a distinct, proper, and ordered naming, as regards the common form, although in the time of the primitive Church it could be done in the name of Christ, in which the understanding of the Trinity is enclosed.