In Scripture the Holy Spirit says: "By works of mercy and by faith sins are purged." [Prov. 16.6] This cannot possibly refer to sin committed before our redemption, for they are purged by the blood of Christ and by sanctification.
Many and great are the blessings which have been and are being ever bestowed on us for our salvation by the boundless mercy of God the Father and Christ. The Father sent the Son to restore us by saving us and giving us life. The Son was content to be sent and to be called Son of Man in order to make us children of God. He humbled himself to exalt a people who were prostrate; he was wounded to heal our wounds; he became a slave to bring to liberty those who were slaves; he underwent death that he might procure immortality for mortals. Such is the measure and the extent of the gifts of the divine love.
But God's providence and God's mercy are not yet fully told. In the plan of our salvation there is provision of still greater care for the preservation of humankind after our redemption. Just as remission of sins is given once for all in baptism, so unremitting and ceaseless service fulfills a role similar to that of baptism by bestowing yet again the mercy of God. The merciful one tells us to do acts of mercy, and, because he wants to preserve those redeemed at so great a cost, he teaches us how we can be cleansed once more if we become defiled after receiving the grace of baptism.
In conclusion, the divine admonition never rests, is never silent. In the Holy Scriptures, both old and new, the people of God at all times and in all places are stirred up to works of mercy. Everyone who is being prepared for the hope of the kingdom of heaven is commanded by the voice and counsel of the Holy Spirit to give alms.
from On Works and Almsgiving (written c. 253)