Obj. 2: Further, John the Baptist received special commendation from Christ, Who said of him (Matt. 11:11): "There hath not risen among them that are born of women, a greater than John the Baptist." But those whom John had baptized were baptized again, according to Acts 19:1-7, where it is stated that Paul rebaptized those who had received the Baptism of John. Much more, therefore, should those be rebaptized, who have been baptized by heretics or sinners.
Obj. 3: Further, it was decreed in the Council of Nicaea (Can. xix) that if "any of the Paulianists or Cataphrygians should be converted to the Catholic Church, they were to be baptized": and this seemingly should be said in regard to other heretics. Therefore those whom the heretics have baptized, should be baptized again.
Obj. 4: Further, Baptism is necessary for salvation. But sometimes there is a doubt about the baptism of those who really have been baptized. Therefore it seems that they should be baptized again.
Obj. 5: Further, the Eucharist is a more perfect sacrament than
Baptism, as stated above (Q. 65, A. 3). But the sacrament of the
Eucharist is reiterated. Much more reason, therefore, is there for
Baptism to be reiterated.
On the contrary, It is written, (Eph. 4:5): "One faith, one Baptism."
I answer that, Baptism cannot be reiterated.
First, because Baptism is a spiritual regeneration; inasmuch as a man dies to the old life, and begins to lead the new life. Whence it is written (John 3:5): "Unless a man be born again of water and the Holy Ghost, He cannot see [Vulg.: 'enter into'] the kingdom of God." Now one man can be begotten but once. Wherefore Baptism cannot be reiterated, just as neither can carnal generation. Hence Augustine says on John 3:4: "'Can he enter a second time into his mother's womb and be born again': So thou," says he, "must understand the birth of the Spirit, as Nicodemus understood the birth of the flesh . . . . As there is no return to the womb, so neither is there to Baptism."
Secondly, because "we are baptized in Christ's death," by which we die unto sin and rise again unto "newness of life" (cf. Rom. 6:3, 4). Now "Christ died" but "once" (Rom. 6:10). Wherefore neither should Baptism be reiterated. For this reason (Heb. 6:6) is it said against some who wished to be baptized again: "Crucifying again to themselves the Son of God"; on which the gloss observes: "Christ's one death hallowed the one Baptism."
Thirdly, because Baptism imprints a character, which is indelible, and is conferred with a certain consecration. Wherefore, just as other consecrations are not reiterated in the Church, so neither is Baptism. This is the view expressed by Augustine, who says (Contra Epist. Parmen. ii) that "the military character is not renewed": and that "the sacrament of Christ is not less enduring than this bodily mark, since we see that not even apostates are deprived of Baptism, since when they repent and return they are not baptized anew."
Fourthly, because Baptism is conferred principally as a remedy against original sin. Wherefore, just as original sin is not renewed, so neither is Baptism reiterated, for as it is written (Rom. 5:18), "as by the offense of one, unto all men to condemnation, so also by the justice of one, unto all men to justification of life."