A.T. Robertson Commentary John 1:26

"John answered them, saying, I baptize in water: in the midst of you standeth one whom ye know not," — John 1:26 (ASV)

In the midst of you standeth (μεσος υμων στηκε). Adjective as in 19:18, not εν μεσω υμων. Present active indicative of late verb στηκω from perfect stem εστηκα. John had already baptized Jesus and recognized him as the Messiah.

Whom ye know not (ον υμεις ουκ οιδατε). This was the tragedy of the situation (1:11). Apparently this startling declaration excited no further inquiry from the committee.