John Gill 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 Jesus as he walked
Either by them; or as he was going from them to his lodgings; it being toward the close of the day, when John had finished his work for that day, and the people were departing home: John fixed his eyes intently on Christ, with great pleasure and delight, and pointing at him,

he says, behold the Lamb of God ;
as in (John 1:29) , where it is added, "which takes away the sin of the world"; and which the Ethiopic version subjoins here.