John 1:31

31. κἀγὼ οὐκ ἤδειν αὐτόν. I also knew Him not; I, like you (John 5:26), did not at first know Him to be the Messiah. This does not contradict Matthew 3:14. (1) ‘I knew Him not’ need not mean ‘I had no knowledge of Him whatever.’ (2) John’s declaration of his need to be baptized by Jesus does not prove that he had already recognized Jesus as the Messiah, but only as superior to himself.

ἀλλ' ἵνα. See on John 1:8. This is the second half of the Divine purpose respecting the Baptist. He was (1) to prepare for the Messiah by preaching repentance; (2) to point out the Messiah.

φανερωθῇ. One of S. John’s favourite words; John 2:11; John 3:21; John 7:4; John 9:3; John 17:6; John 21:1; John 21:14; 1 John 1:2; 1 John 2:19; 1 John 2:28; 1 John 3:2; 1 John 3:5; 1 John 3:8-9; Revelation 3:18; Revelation 15:4. See on John 2:11.

διὰ τοῦτο. For this cause (John 12:18; John 12:27) came I: comp. John 5:16; John 5:18; John 7:22; John 8:47; John 19:11. In translation we must distinguish διὰ τοῦτο from S. John’s favourite particle οὖν.

ἐν [τῷ] ὕδατι. Placed before βαπτίζων for emphasis, because here he contrasts himself as baptizing with water with Him who baptizes with the Holy Spirit.