Passage
On the morrow he seeth Jesus coming unto him, and saith, Behold, the Lamb of God, that taketh away the sin of the world!
John 1:29 (ASV)
Nearby Context
John 1:27 [even] he that cometh after me, the latchet of whose shoe I am not worthy to unloose.
John 1:28 These things were done in Bethany beyond the Jordan, where John was baptizing.
John 1:29 On the morrow he seeth Jesus coming unto him, and saith, Behold, the Lamb of God, that taketh away the sin of the world!
John 1:30 This is he of whom I said, After me cometh a man who is become before me: for he was before me.
John 1:31 And I knew him not; but that he should be made manifest to Israel, for this cause came I baptizing in water.
Study Lenses
The verse centers on "world", "morrow", "seeth", "jesus", "coming", "saith", "behold", and "lamb". It is saying that the verse draws attention to "world" and "morrow", so its meaning should be read from those terms before moving to application.
The nearby context moves from verse 28's "These things were done in Bethany beyond..." into verse 30's "This is he of whom I said...", so "world" and "morrow" belong inside that flow. In John context, the local focus is the identity of Jesus, new birth, eternal life, and belief and unbelief.
A plain takeaway is to answer the verse's own emphasis on "world" and "morrow" with trust shaped by these words, not by a vague optimism outside the passage.