31 What power, O robber, led you to the light? Who taught you to worship that despised Man, your companion on the Cross? O Light Eternal, which gives light to them that are in darkness! Therefore also he justly heard the words, Be of good cheer; not that your deeds are worthy of good cheer; but that the King is here, dispensing favours. The request reached unto a distant time; but the grace was very speedy. Verily I say unto you, This day shall you be with Me in Paradise; because today you have heard My voice, and hast not hardened your heart. Very speedily I passed sentence upon Adam, very speedily I pardon you.
To him it was said, In the day wherein you eat, you shall surely die; but thou today hast obeyed the faith, today is your salvation. Adam by the Tree fell away; thou by the Tree art brought into Paradise. Fear not the serpent; he shall not cast you out; for he is fallen from heaven. And I say not unto you, This day shall you depart, but, This day shall you be with Me. Be of good courage: you shall not be cast out. Fear not the flaming sword; it shrinks from its Lord. O mighty and ineffable grace!
The faithful Abraham had not yet entered, but the robber enters! Moses and the Prophets had not yet entered, and the robber enters though a breaker of the law. Paul also wondered at this before you, saying, Where sin abounded, there grace did much more abound. They who had borne the heat of the day had not yet entered; and he of the eleventh hour entered. Let none murmur against the goodman of the house, for he says, Friend, I do you no wrong; is it not lawful for Me to do what I will with My own?
The robber has a will to work righteousness, but death prevents him; I wait not exclusively for the work, but faith also I accept. I have come who feed My sheep among the lilies, I have come to feed them in the gardens. I have found a sheep that was lost, but I lay it on My shoulders; for he believes, since he himself has said, I have gone astray like a lost sheep; Lord, remember me when You come in Your kingdom.
Source: Catechetical Lectures (New Advent)