Adam Clarke on Mark 1:8

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, Luk 3:16.