Acts 19:3

And he said unto them, unto what then were ye baptized?
&c.] The apostle takes it for granted that they were baptized, since they were not only believers, but disciples; such as not only believed with the heart, but had made a profession of their faith, and were followers of Christ; but asks unto what they were baptized; either in whose name they were baptized, since Christian baptism was administered in the name of the Spirit, as well as in the name of the Father and of the Son; or what attended or followed their baptism, seeing sometimes the Holy Ghost fell upon persons, either before baptism, or at it, or after it:

and they said, unto John's baptism;
some think they had never been baptized at all with water baptism, only had received the doctrine preached by John, concerning repentance and remission of sins, and so were baptized unto him, professing the same doctrine he did, just as the Israelites were baptized into Moses; others think they were baptized, but very wrongly, being baptized in the name of John, and not in the name of Jesus Christ; and so, as it was not Christian baptism they had submitted to, it was right to baptize them again: but neither of these are probable, for it is not likely that they should receive John's doctrine, and not his baptism; that they should be his disciples and followers, and not attend to the more distinguishing branch of his ministry; and it is still more unlikely that they should be baptized in his name, who preached Jesus Christ to his followers, and pointed out to them the Lamb of God, and declared him to be greater than he; it seems rather that they were baptized, and that they were baptized in the name of Christ, as John's disciples were, as the apostle affirms in the following words.