After the strong warning in Leviticus 6:9–10, Paul reassures his readers of their true conversion.
But you were washed: (see Acts 22:16) Cleanliness symbolizes the righteousness that comes from forgiveness (see Titus 3:5). God himself made them holy (see 1 Corinthians 1:2).
They became right with God through their connection with the Lord Jesus Christ and the transformative work of the Spirit of our God. God forgave them. He views them as righteous (see Romans 1:17; 3:21–26), and their lives have truly improved (see Titus 3:5–7).