Objection 1. It would seem that if a man fall into sin after being contrite for all his sins, he can, now that he has lost charity, satisfy for his other sins which were already pardoned him through his contrition. For Daniel said to Nabuchodonosor (Daniel 4:24): "Redeem thou thy sins with alms." Yet he was still a sinner, as is shown by his subsequent punishment. Therefore a man can make satisfaction while in a state of sin.
Objection 2. Further, "Man knoweth not whether he be worthy of love or hatred" (Ecclesiastes 9:1). If therefore one cannot make satisfaction unless one be in a state of charity, it would be impossible to know whether one had made satisfaction, which would be unseemly.
Objection 3. Further, a man's entire action takes its form from the intention which he had at the beginning. But a penitent is in a state of charity when he begins to repent. Therefore his whole subsequent satisfaction will derive its efficacy from the charity which quickens his intention.
Objection 4. Further, satisfaction consists in a certain equalization of guilt to punishment. But these things can be equalized even in one who is devoid of charity. Therefore, etc.
On the contrary, "Charity covereth all sins" (Proverbs 10:12). But satisfaction has the power of blotting out sins. Therefore it is powerless without charity.
Further, the chief work of satisfaction is almsdeeds. But alms given by one who is devoid of charity avail nothing, as is clearly stated 1 Corinthians 13:3, "If I should distribute all my goods to feed the poor... and have not charity, it profiteth me nothing." Therefore there can be no satisfaction with mortal sin.
I answer that, Some have said that if, when all a man's sins have been pardoned through contrition, and before he has made satisfaction for them, he falls into sin, and then makes satisfaction, such satisfaction will be valid, so that if he die in that sin, he will not be punished in hell for the other sins.
But this cannot be, because satisfaction requires the reinstatement of friendship and the restoration of the equality of justice, the contrary of which destroys friendship, as the Philosopher states (Ethic. ix, 1,3). Now in satisfaction made to God, the equality is based, not on equivalence but rather on God's acceptation: so that, although the offense be already removed by previous contrition, the works of satisfaction must be acceptable to God, and for this they are dependent on charity. Consequently works done without charity are not satisfactory.
Reply to Objection 1. Daniel's advice meant that he should give up sin and repent, and so make satisfaction by giving alms.
Reply to Objection 2. Even as man knows not for certain whether he had charity when making satisfaction, or whether he has it now, so too he knows not for certain whether he made full satisfaction: wherefore it is written (Sirach 5:5): "Be not without fear about sin forgiven." And yet man need not, on account of that fear, repeat the satisfaction made, if he is not conscious of a mortal sin. For although he may not have expiated his punishment by that satisfaction, he does not incur the guilt of omission through neglecting to make satisfaction; even as he who receives the Eucharist without being conscious of a mortal sin of which he is guilty, does not incur the guilt of receiving unworthily.
Reply to Objection 3. His intention was interrupted by his subsequent sin, so that it gives no virtue to the works done after that sin.
Reply to Objection 4. Sufficient equalization is impossible both as to the Divine acceptation and as to equivalence: so that the argument proves nothing.
Source: Summa Theologica (New Advent)