(Recapitulation.) “And they came to Ephesus, and there he left them”: for he did not wish to take them about with him, but left them at Ephesus. But they subsequently dwelt at Corinth, and he bears high testimony to them, and writing to the Romans, salutes them. Whence it seems to me that they afterwards went back to Rome, in the time of Nero, as having an attachment for those parts whence they had been expelled in the time of Claudius. “But he himself went into the synagogue.”
It seems to me that the faithful still assembled there, for they did not immediately withdraw them. “And when they besought him to stay, he consented not”, for he was hastening to Cæsarea. “And having arrived at Cæsarea,” etc., “passing through the region of Galatia and Phrygia, confirming all the disciples.” (v. 22, 23.) Through these regions also he merely passes again, just enough to establish them by his presence. “And a certain Jew, Apollos by name,” etc. For he was an awakened man, travelling in foreign parts for this very purpose.
Writing of him the Apostle said, “Now concerning Apollos our brother.” (β ) “Whom when Aquila and Priscilla had heard,” etc. It was not for nothing that he left them at Ephesus, but for Apollos' sake, the Spirit so ordered it, that he might come with greater force to the attack (ἑ πιβἥναι) upon Corinth. What may be the reason that to him they did nothing, but Paul they assault? They knew that he was the leader, and great was the name of the man.
“And when he was disposed to pass into Achaia” i.e. in faith, he did all by faith; “the brethren wrote,” etc. nowhere envy, nowhere an evil eye. Aquila teaches, or rather this man lets himself be taught. He was minded to depart, and they send letters. (a) “For he mightily convinced the Jews, and that publicly,” etc. Now by this, that he “publicly” convinced them, his boldness was shown: by the clearness of his arguing, his power was declared: by his convicting them out of the Scriptures, his skill (of learning).
For neither boldness by itself contributes anything, where there is not power, nor power where there is not boldness. “He mightily convinced,” it says. (β ) “And it came to pass,” etc. But whence had those, being in Ephesus, the baptism of John? Probably they had been on a visit at Jerusalem at the time (of John's preaching), and did not even know Jesus. And he does not say to them, Do ye believe in Jesus? But what? “Have ye received the Holy Ghost?” He knew that they had not, but wishes themselves to say it, that having learned what they lack, they may ask.
“John verily baptized,” etc. From the baptism itself he (John) prophesies: and he leads them (to see) that this is the meaning of John's baptism. (a) “That they should believe in Him that was to come:” on what kind (of Person)? “I indeed baptize you with water, but He that comes after me, shall baptize you with the Holy Ghost.” “And when Paul,” it says, “had laid his hands upon them, the Holy Ghost came on them; and they spoke with tongues, and prophesied.” (β ) The gift is twofold: tongues and prophesyings.
Hence is shown an important doctrine, that the baptism of John is incomplete. And he does not say, “Baptism” of forgiveness, but, “of repentance.” What (is it) then? These had not the Spirit: they were not so fervent, not even instructed. And why did (Apollos) not receive baptism? (The case) seems to me to be this: Great was the boldness of the man. “He taught diligently the things concerning Jesus,” but he needed more diligent teaching. Thus, though not knowing all, by his zeal he attracted the Holy Ghost, in the same manner as Cornelius and his company.
Source: Homilies on Acts (New Advent)