Treasury of Scripture Knowledge

Summary

And I knew him not: but that he should be made manifest to Israel, therefore am I come baptizing with water.

Bible References

I knew

John 1:33
And I did not recognize Him, but He [i.e., God], who sent me to immerse in water, said to me, 'The one on whom you see the Holy Spirit descending and remaining is the same One who [will] immerse people in the Holy Spirit.'
Luke 1:80
So, the child [i.e., John] grew and became strong in [his] spirit and stayed in the desert until the day when he appeared publicly to the Israelites.
Luke 2:39
So, when Joseph and Mary had completed everything required by the law of the Lord, they returned to their [current home] town of Nazareth, in Galilee.

But

John 1:7
He came to be a witness, so that he might testify concerning that Light, so that all people would believe [in Jesus] through him [i.e., through his testimony. See Acts 19:4].
Luke 1:17
He will go on ahead of the Messiah [See verse 76], in the spirit and power of Elijah, to rekindle the affections of fathers for their children, and [to influence] disobedient people to live wisely like righteous people. And he will prepare the people to be ready for [the coming of] the Lord."

Therefore

Matthew 3:6
and people were immersed by him in the Jordan River as they confessed their sins.
Mark 1:3
from Isa. 40:3], "Look, I am sending my messenger on ahead of you. He will prepare the way for you.
Luke 3:3
He went into the whole region around the Jordan River proclaiming that those immersed on the basis of their repentance [i.e., determining to change their hearts and lives] would receive the forgiveness of sins [from God].
Acts 19:4
Paul [then] said, "John immersed people who [demonstrated their] repentance, telling them they must believe in Jesus, the One who would come after him."