Cyril of Jerusalem

So then the prophet comforted David as we have seen, but that blessed man, though he received most gladly the assurance, "The Lord has put away your sin," did not, king as he was, draw back from penitence. Indeed he put on sackcloth in place of his purple robe, and the king sat in ashes on the bare earth instead of on his gilded throne. And in ashes he did not merely sit but took them for eating, as he himself says, "I have eaten ashes as if bread and mingled my drink with weeping." His lustful eye he wasted away with tears; as he says, "Every night I wash my bed and water my couch with my tears." And when his courtiers exhorted him to take bread, he would not, but he prolonged his fast for seven whole days. Now if a king was apt to make confession after this manner, should not you, as a private person, make your confession? Again, after Absalom's rebellion, when David was in flight, with many roads to choose from before him, he chose to make his escape by the Mount of Olives, as good as invoking in his own mind the Deliverer who should from there ascend into the heavens. And when Shimei cursed him bitterly, he said, "Let him be." For he knew that forgiveness is for those who forgive.