Jamieson, Fausset and Brown on 1 Corinthians 1:14

14. I thank God's providence now, who so ordered it that I baptized none of you but Crispus (the former ruler of the synagogue, Ac 18:8) and Gaius (written by the Romans Caius, the host of Paul at Corinth, and of the church, Ro 16:23; a person therefore in good circumstances). Baptizing was the office of the deacons (Ac 10:48) rather than of the apostles, whose office was that of establishing and superintending generally the churches. The deacons had a better opportunity of giving the necessary course of instruction preparatory to baptism. Crispus and Gaius were probably among the first converts, and hence were baptized by Paul himself, who founded the church.