but the end of the charge is love, out of a pure heart and a good conscience and unfeigned faith;

 Paul's Jewish background comes out. He says that Jesus Christ had mercy on him because he committed his sins against Christ and his Church in the days of his ignorance. We often think that the Jewish viewpoint was that sacrifice atoned for sin; a man sinned, his sin broke his relationship with God, then sacrifice was made and God's anger was appeased and the relationship restored. 