Acts 19:4-5, 18

Paul said, “John performed a baptism of repentance, continually telling the people to believe in Him who was coming after him, that is, [to confidently accept and joyfully believe] in Jesus [the Messiah and Savior].” After hearing this, they were baptized [again, this time] in the name of the Lord Jesus.

Many of those who had become believers were coming, confessing and disclosing their [former sinful] practices.