This man was instructed in the way of the Lord; and being fervent in the spirit, he spake and taught diligently the things of the Lord, knowing only the baptism of John. This man was instructed in the way of the Lord - Κατηχημενος; He was catechized, initiated, in the way, the doctrine, of Jesus as the Christ.
Being fervent in the spirit - Being full of zeal to propagate the truth of God, he taught diligently, ακριβως accurately, (so the word should be translated), the things of Christ as far as he could know them through the ministry of John the Baptist; for it appears he knew nothing more of Christ than what John preached. Some suppose we should read ουκ, not, before ακριβως, correctly, or accurately, because it is said that Aquila and Priscilla expounded the way of the Lord, ακριβεϚερον, more perfectly, rather more accurately; but of this emendation there is not the slightest necessity; for surely it is possible for a man to teach accurately what he knows; and it is possible that another, who possesses more information on the subject than the former, may teach him more accurately, or give him a larger portion of knowledge. Apollo knew the baptism of John; but he knew nothing farther of Jesus Christ than that baptism taught; but, as far as he knew, he taught accurately. Aquila and Priscilla were acquainted with the whole doctrine of the Gospel: the doctrine of Christ dying for our sins, and rising again for our justification; and in this they instructed Apollo; and this was more accurate information than what he had before received, through the medium of John's ministry.