Penance

Penance is a necessity for those who are far away, that they may draw near.  For it is, as Jerome says, “a second plank after a shipwreck,” because if anyone, by sinning, should corrupt the vesture of innocence received in baptism, it can be repaired by the remedy of penance.  The first plank is baptism, whereby the old man is put off and the new man put on; the second, penance, by which we raise ourselves again after a fall, while the old garment is put away again and the new garment, which was lost, is resumed.  The erring can be renewed after baptism through penance, but not through baptism; a man may do penance often, but he may not be baptized often.  Baptism is a sacrament only, but penance is said to be both a sacrament and a virtue of the mind.  For there is internal penitence and an external penance: the external is the sacrament, the internal is a virtue of the mind.  Each of these is a cause of health and of justification.…  The preaching of John started from penance, when he said, “Do penance: for the kingdom of heaven is at hand.”  “Moreover the herald taught what the Truth afterward preached; for he began his sermon with penance.”

– from Sentences, Book IV, Distinction XIV (c. 1150), by Peter Lombard (c. 1096–1160)