Luke 3:3
"And he came into all the country about Jordan, preaching the baptism of repentance for the remission of sins;"
Cross References (ranked by relevance)
To give knowledge of salvation unto his people by the remission of their sins,
When John had first preached before his coming the baptism of repentance to all the people of Israel.
And they came unto John, and said unto him, Rabbi, he that was with thee beyond Jordan, to whom thou barest witness, behold, the same baptizeth, and all men come to him.
And now why tarriest thou? arise, and be baptized, and wash away thy sins, calling on the name of the Lord.
Then said Paul, John verily baptized with the baptism of repentance, saying unto the people, that they should believe on him which should come after him, that is, on Christ Jesus.
I indeed baptize you with water unto repentance: but he that cometh after me is mightier than I, whose shoes I am not worthy to bear: he shall baptize you with the Holy Ghost, and with fire:
These things were done in Bethabara beyond Jordan, where John was baptizing.