Charles Ellicott Commentary John 1:36

"and he looked upon Jesus as he walked, and saith, Behold, the Lamb of God!" — John 1:36 (ASV)

And looking upon.—Better, and he looked upon Jesus as He was walking, and says. The word “looked upon” expresses a fixed, earnest gaze. (Matthew 19:26; Mark 10:21; Mark 10:27; etc.) At this look, all the old thoughts in their fullness come crowding back. Yes. It is He. Behold the Lamb of God!