8 Finally, after the redemption from all corruption, what remains but the crown of righteousness? This at least remains, but even in it, or under it, let not the head be swollen that it may receive the crown. Hear, mark well the Psalm, how that crown will not have a swollen head. After he had said, “Who redeems your life from corruption;” he says, “Who crowns you.” Here you were ready at once to say, “'Crowns you,' is an acknowledgment of my merits, my own excellence has done it; it is the payment of a debt, not a gift.”
Give ear rather to the Psalm. For it is you again that sayest this; and “all men are liars.” Hear what God says; “Who crowns you with mercy and pity.” Of His mercy He crowns you, of His pity He crowns you. For you had no worthiness that He should call you, and being called should justify you, being justified glorify you. “The remnant is saved by the election of grace. But if by grace, then is it no more of works; otherwise grace is no more grace. For to him that works, the reward shall not be reckoned according to grace, but according to debt.” The Apostle says, “Not according to grace, but according to debt.” But “you He crowns with pity and mercy;” and if your own merits have gone before, God says to you, “Examine well your merits, and you shall see that they are My gifts.”
Source: Sermons on Selected Lessons of the New Testament (New Advent)