Augustine discusses true repentance as he explores Psalm 51, David’s expression of sorrow for sin and a contrite heart.
I acknowledge my transgression, says David. If I admit my fault, then you will pardon it. Let us never assume that if we live good lives we will be without sin; our lives should be praised only when we continue to beg for pardon. But men are hopeless creatures, and the less they concentrate on their own sins, the more interested they become in the sins of others. They seek to criticize, not to correct. Unable to excuse themselves, they are ready to accuse others.
This was not the way that David showed us how to pray and make amends to God, when he said: I acknowledge my transgression, and my sin is ever before me. He did not concentrate on others’ sins; he turned his thoughts on himself. He did not merely stroke the surface, but he plunged inside and went deep down within himself. He did not spare himself, and therefore was not impudent in asking to be spared.
Do you want God to be appeased? Learn what you are to do that God may be pleased with you. Consider the psalm again: If you wanted sacrifice, I would indeed have given it; in burnt offerings you will take no delight. Are you then to be without sacrifice? Are you to offer nothing? Will you please God without an offering?
Consider what you read in the same psalm: If you wanted sacrifice, I would indeed have given it; in burnt offerings you will take no delight. But continue to listen, and say with David: A sacrifice to God is a contrite spirit; God does not despise a contrite and humble heart. Cast aside your former offerings, for now you have found out what you are to offer. In the days of your fathers you would have made offerings of cattle – these were the sacrifices. If you wanted sacrifice, I would indeed have given it. These then, Lord, you do not want, and yet you do want sacrifice.
You will take no delight in burnt offerings, David says. If you will not take delight in burnt offerings, will you remain without sacrifice? Not at all. A sacrifice to God is a contrite spirit; God does not despise a contrite and humble heart.
You now have the offering you are to make. No need to examine the herd, no need to outfit ships and travel to the most remote provinces in search of incense. Search within your heart for what is pleasing to God. Your heart must be crushed. Are you afraid that it might perish so? You have the reply: Create a clean heart in me, O God. For a clean heart to be created, the unclean one must be crushed.
We should be displeased with ourselves when we commit sin, for sin is displeasing to God. Sinful though we are, let us at least be like God in this, that we are displeased at what displeases him. In some measure then you will be in harmony with God’s will, because you find displeasing in yourself what is abhorrent to your Creator.
These words commenting on David’s contrite confession of his transgression and sin in Psalm 51 are an excerpt from St. Augustine’s Sermon 19, 2-3: CCL 41, 252-254 and are used in the Roman Catholic Office of Readings for the 14th Sunday of Ordinary Time with the accompanying biblical reading taken from 2 Samuel 12:1-25, the response of King David to Nathan who confronts him about his sins aganist Uriah and Bathsheba.