Adam Clarke on John 1:26

I baptize with water - See on Mar 1:8 (note). I use the common form, though I direct the baptized to a different end, viz. that they shall repent of their sins, and believe in the Messiah.

There standeth one among you - That is, the person whose forerunner I am is now dwelling in the land of Judea, and will shortly make his appearance among you. Christ was not present when John spoke thus, as may be seen from Joh 1:29.