Part — Wouters, Manual of Moral Theology
Part I. On the Existence of the Sacrament of Baptism
Baptism is a true sacrament of the New Law. This is of faith from the Council of Trent,1 and it is clear from Sacred Scripture, which openly teaches that Baptism is a sensible sign instituted by Christ and efficacious of grace.
I said a sensible sign, that is, consisting of matter, which is washing with water, and of form, which is situated in the invocation of the Most Holy Trinity. It suffices to have alleged John 3:5: Unless one is born again of water and the Holy Spirit, he cannot enter into the kingdom of God; and Matthew 28:19: Going therefore, teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Spirit.
I said a sign efficacious of grace; since regeneration, concerning which Matthew speaks in the cited place, cannot be understood except as spiritual regeneration, which is effected through grace. For the rest, let the dogmatic theologians be consulted.
Note 1. It is disputed concerning the time at which Christ instituted Baptism. The more common and more probable opinion teaches that it was instituted by Christ before the Passion. Otherwise the Apostles would have received the Holy Eucharist and Order before Baptism had been received. There is added that the disciples of Christ baptized before the Passion of the Master.2 Now the Baptism conferred by the disciples seems to have been different from the Baptism of John the Baptist. This is deduced from John 3:25 ff. It remains, therefore, that we say that the Baptism conferred by the disciples of Christ was our sacrament. For a third Baptism is invented without sufficient reason (St. Thomas, III, q. 66, a. 2; St. Alphonsus, VI, 96).
It is more disputed at what precise moment Christ instituted Baptism. According to some, in the discourse with Nicodemus;3 according to others, when He sent the disciples to baptize.4 According to St. Thomas (III, q. 66, a. 2 and q. 73, a. 5, ad 4), St. Alphonsus (VI, 96), and others, when He Himself was baptized by John.5
Note 2. The Baptism of John was not of the same efficacy as the Baptism of Christ. This is of faith from the Council of Trent.6 Further, according to St. Thomas, "the Baptism of John was not of itself a sacrament, but as it were a certain sacramental disposing for the Baptism of Christ, and therefore in some way it belongs to the law of Christ, but not to the law of Moses" (III, q. 38, a. 1, ad 1).
1 Session 7, On Baptism, canon 1.
3 John 3.
6 Session 7, On Baptism, canon 1.