I. Preamble to the Question: That Baptism was Instituted in the New Law is True and Reasonable

133. This question supposes that baptism was instituted in the New Law. And it is true and reasonable.

A. It is True

134. It is true, as is plain from many necessary authorities in the New Testament, of Christ and the Apostles, wherein the necessity of baptism is proved, which would not be the case if baptism had not been legitimately instituted in the [New] Law.

135. However there is doubt about when it was first instituted.

Not indeed when Christ was baptized by John, because that was not a baptism of Christ, that is, according to Christ’s form, but according to John’s form. Yet Christ did then dedicate water, from the contact with it of his most pure flesh, as suitable matter for his baptism, because the use of water was confirmed in the legislator, that is, as a ministry.

136. Nor too was baptism instituted in the words of John 3.5, when the Lord says to Nicodemus, “Unless a man be born again of water etc.,” because it is not likely that so necessary a sacrament was instituted in secret before a private person, who was not due to be a herald of that institution.

137. Nor too was it deferred to the time of the Ascension, Matthew 28.19 [“Go then and teach all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit”], for the disciples were baptizing with the baptism of Christ before the Passion: in John 3.26 the disciples of John say to John, “Rabbi, he to whom you bore witness, behold he is baptizing and all come to him,” and in the following chapter, John 4.1, “Although Jesus did not baptize but his disciples.”

138. The time, then, of the institution is convincingly shown to have been before the time when Christ’s disciples were baptizing, although the hour is not precisely read in the Gospel.

B. It is Reasonable

139. This supposition also seems reasonable, because the principal sacrament of the New Law (namely, that through which entrance is made for its observance) needed to be new and proper to that Law, as was said before in d.1 nn.254-257.

140. This sacrament needed to be evident too in its signification, because this Law is the Law of truth that removes the shadow [cf. Hebrews 10.1].

141. It needed to be rich too in the conferring of grace, because this Law is the Law of grace, John 1.17, “Grace and truth were brought about through Jesus Christ.”

142. It needed to be easy too, because the yoke of Christ is pleasant and his burden light, Matthew 11.30.

143. It needed also to be common, because God chose for the Mosaic Law one people only, but for the New Law he chose the whole world, according to Psalm 18/19.4, “Their sound has gone out to all the earth.”

144. These five features [nn.139-143] are found in one thing, namely in the washing of baptism and its words, because it clearly signifies the cleansing of the soul, which is the principal effect, and copiously bestows grace. Hence in Psalm 22/23.2 it speaks of the waters of repose, “beside the waters of repose.” The washing of baptism is also easy, because it is in no way dangerous (as circumcision is), and is common to every sex and age.