Passage
And I knew him not: but that he may be made manifest in Israel, therefore am I come baptizing with water.
John 1:31 (DRB)
Nearby Context
John 1:29 The next day, John saw Jesus coming to him; and he saith: Behold the Lamb of God. Behold him who taketh away the sin of the world.
John 1:30 This is he of whom I said: After me there cometh a man, who is preferred before me: because he was before me.
John 1:31 And I knew him not: but that he may be made manifest in Israel, therefore am I come baptizing with water.
John 1:32 And John gave testimony, saying: I saw the Spirit coming down, as a dove from heaven; and he remained upon him.
John 1:33 And I knew him not: but he who sent me to baptize with water said to me: He upon whom thou shalt see the Spirit descending and remaining upon him, he it is that baptizeth with the Holy Ghost.
Study Lenses
The verse centers on "knew", "manifest", "israel", "therefore", "come", "baptizing", and "water". It is saying that the verse draws attention to "knew" and "manifest", so its meaning should be read from those terms before moving to application.
The nearby context moves from verse 30's "This is he of whom I said..." into verse 32's "And John gave testimony saying I saw...", so "knew" and "manifest" 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 "knew" and "manifest" with trust shaped by these words, not by a vague optimism outside the passage.