Theophylact of Ohrid

The Evangelist, hinting at the slander of the envious, says that although Jesus did not baptize, nevertheless the envious, wishing to incite the Pharisees against Christ, slandered Him by saying that He was baptizing.

Commentary on John ↗

Augustine of Hippo

Truly had the Pharisees' knowledge that our Lord was making more disciples, and baptizing more than John, been such as to lead them heartily to follow Him, He would not have left Judaea, but would have remained for their sake: but seeing, as He did, that this knowledge of Him was coupled with envy, and made them not followers, but persecutors, He departed thence. …

Catena Aurea by Aquinas ↗

Thomas Aquinas

Having set forth the teaching of Christ on spiritual regeneration, and that Christ had given this grace of spiritual regeneration to the Jews, he now shows how Christ gave this grace to the Gentiles. Now the salutary grace of Christ had been dispensed in two ways to the Gentiles: through teaching and through miracles. "Going forth, they preached everywhere": this is the teaching; "the Lord cooperated with them, and confirmed the word with signs". These are the miracles (Mk 16:20). …

Commentary on John ↗

Bonaventure

The Lord manifested himself above to the disciples and to the Jews: in this part he manifests himself to the Samaritans, and this by preaching and announcing to them the word of salvation. And this part has two parts. In the first is noted the opportunity for preaching: in the second, the form of preaching, at: "A woman of Samaria came," where the Lord begins to preach to the Samaritan woman. Now the opportunity was on the part of the place, and this indeed was twofold, namely for passing through and for resting. …

Commentary on John, Chapter 4 ↗