I indeed have baptized you with water - As if he had said: This baptism is not to be rested in; it is only an emblem of that which you must receive from him who is mightier than I. It is he only who can communicate the Holy Spirit; and water baptism is nothing, but as it points out, and leads to, the baptism of the Holy Ghost. The subject of these two verses is not found in Matthew nor John; but is mentioned with some varying circumstances by Luke, Luke 3:16.

I indeed have (f) baptized you with water: but he shall baptize you with the Holy Ghost.
(f) He shows that all the power of baptism proceeds from Christ, who baptizes the inner man.

I indeed have baptized you with water,.... This was spoken to the baptized persons, partly to take off their dependence upon him and his baptism; and partly to direct their views to Christ, from whom the gifts and graces of the Spirit are alone to be had:
but he shall baptize you with the Holy Ghost; See Gill on Matthew 3:11. One copy adds, "and with fire", as there: a Jewish writer says, the holy blessed God baptizeth with fire, and the wise shall understand (p).
(p) R. Menachem in Leviticus. viii. apud Ainsworth on Genesis. xvii. 12.