God Does Not Demand Penance
God does not expect penance, a specific time of self-punishment and self-denial set aside to suffer for your sins. You aren't required to do something before you can be accepted and forgiven. Before the coming of Christ and His placing Himself between our sin and us, taking the full weight and punishment of our guilt on the cross, there was a system in the Hebrew temple for bringing sacrifices before God to atone for the guilt of sin. God set that up through Moses, but He was teaching the people and preparing them for something better: one sacrifice that would take away the guilt of sin forever. The offering of doves and goats on the altar never actually removed the guilt of sin; it was symbolic. (See Hebrews 10:1-18). It pointed the way to the real sacrifice that removed all guilt: Christ. (Hebrews 9:11-15).
Now that Christ has borne our guilt and iniquity, and taken all the penalty of sin onto Himself, there is no purpose for sacrificial offerings anymore. (Hebrews 9:25-28). "For by a single offering he has perfected for all time those who are being sanctified." (Heb. 10:14). "Therefore he is the mediator of a new covenant, so that those who are called may receive the promised eternal inheritance, since a death has occurred that redeems them from the transgressions committed under the first covenant." (Heb. 9:15). "He has no need, like those high priests, to offer sacrifices daily, first for his own sins and then for those of the people, since he did this once for all when he offered up himself." (Heb. 7:27).
Therefore, there is nothing at all to pay. No penance is needed to compensate for sin. Christ already paid it. And as Charles Spurgeon brilliantly said, God is not unjust: what has been paid already, He will never demand to be paid twice. You are not expected by God to take part in paying some of the penalty for your sins. Not even an ounce.
Our biggest difficulty in accepting this is usually that it simply seems too easy. We find it hard to believe that after we've done something shameful or hurtful, God forgives us completely for free. It simply makes more sense to our worldly minds that we should have to pay to get it. Otherwise, can't we just take advantage of God's kindness and do whatever we want? No, because God does expect a couple of things, things that are impossible for people trying to take advantage of His kindness. They are not penance or payment. They are regret and repentance.
Instead, Bring a Broken and Contrite Heart
David makes it clear: "The sacrifices of God are a broken spirit; a broken and contrite heart, O God, you will not despise." (Psalm 51:17). The only thing you must bring is a heart that is sorrowful over sin and repentant. You don't have to do something to be forgiven. But it is necessary that you feel something and believe something. If you regret your sin and desire to be healed, you're ready to come to God. But if you are making a show of asking for forgiveness, while smirking on the inside that you're getting away with something, you're in serious trouble. (I examined what it means to have sincere repentance here.)
If you have any doubt that having a repentant heart is enough to be healed even from serious or destructive sins, consider when David wrote Psalm 51. It was after he had committed adultery with Bathsheba and had her husband Uriah, a faithful soldier serving David, murdered in order to cover it up. Christ did not die on the cross only for little sins. He paid for it all.
Even knowing that, many of us still feel that some period of shame and penance is needed just to be decent and respectful. It feels scandalous to turn around and embrace God's mercy so quickly. It doesn't seem to take sin seriously enough. Part of this is a confusion of emotions. Feeling ashamed and beating yourself up isn't helpful or necessary, but it is perfectly appropriate to feel sorrow and to mourn over sin. We should take the evil of sin seriously, and give thought to how we have dishonored God and harmed or betrayed others by choosing to sin. Sometimes our heartbreak over sin should be very deep and intense, leaving a lasting impact that makes us see sin more clearly and be repulsed by it. But that should not mean we sit far off from God, feeling ashamed to enter His presence until we have grieved long enough. You can remain sorrowful and regretful over sin without waiting before receiving the gift of mercy and comfort from God. The only thing we should slow down for is making sure our heart is actually repentant, so that we come to God sincerely.
How Long Does God Imply We Should Wait Before Seeking Forgiveness?
If that doubtful feeling that it's not okay to ask God for forgiveness right away still lingers, consider this: God's ordinary way of dealing with us when we confess our sins is immediate acceptance and restoration.
The prodigal son returns home, and doesn't even get the words "Father, I have sinned..." out of his mouth before his father grabs him and embraces him. When he does make his plea to be accepted as a servant and work for his bread, his father ignores it completely and immediately restores him as a son and celebrates his return. (Luke 15:11-32). This is Jesus describing God the Father's heart for sinners.
Stop and reflect on how overwhelming this love and acceptance is: the father doesn't even pause to talk it over. He rushes on so that they won't waste a moment when they can be comforting each other and taking joy in being reconciled again.
Paul even says that forgiving everything and releasing this person from sorrow is necessary "so that we would not be outwitted by Satan[.]" (2 Cor. 2:11). Keeping people divided by sin and unsure of forgiveness is a demonic mission. One of the biggest problems with thinking you need to put yourself through a period of isolation and shame after having sinned, beating yourself up about how bad you are, is that it does nothing to make you stronger in resisting sin. Instead, it cuts you off from the source of your strength and resilience. Letting this person linger in sorrow any longer is dangerous: it makes him vulnerable. We can't afford to lock ourselves in a dungeon away from God until we feel we have suffered appropriately for sinning. What we need in that very moment is His strength to lean on.
God does not stand far off when we have sinned. He is right next to us, longing to pick us up again. Jesus displays His heart and empathizes with our failures: "For we do not have a high priest who is unable to sympathize with our weaknesses, but one who in every respect has been tempted as we are, yet without sin. Let us then with confidence draw near to the throne of grace, that we may receive mercy and find grace to help in time of need." (Hebrews 4:15-16). Don't hesitate. Run home with confidence.