Matthew 18:21-35 (ESV)
Then Peter came up and said to him, "Lord, how often will my brother sin against me, and I forgive him? As many as seven times?"  Jesus said to him, "I do not say to you seven times, but seventy times seven.
 "Therefore the kingdom of heaven may be compared to a king who wished to settle accounts with his servants.  When he began to settle, one was brought to him who owed him ten thousand talents.  And since he could not pay, his master ordered him to be sold, with his wife and children and all that he had, and payment to be made.  So the servant fell on his knees, imploring him, 'Have patience with me, and I will pay you everything.'  And out of pity for him, the master of that servant released him and forgave him the debt.  But when that same servant went out, he found one of his fellow servants who owed him a hundred denarii, and seizing him, he began to choke him, saying, 'Pay what you owe.'  So his fellow servant fell down and pleaded with him, 'Have patience with me, and I will pay you.'  He refused and went and put him in prison until he should pay the debt.  When his fellow servants saw what had taken place, they were greatly distressed, and they went and reported to their master all that had taken place.  Then his master summoned him and said to him, 'You wicked servant! I forgave you all that debt because you pleaded with me.  And should not you have had mercy on your fellow servant, as I had mercy on you?'  And in anger his master delivered him to the jailers, until he should pay all his debt.  So also my heavenly Father will do to every one of you, if you do not forgive your brother from your heart."
Forgiving. We forgive out of the treasury of God’s forgiveness. I’m always surprised to hear people say man cannot forgive sins. Do they realize they are quoting Pharisees? In anycase, these people often seem as incapable of forgiving as they say man is. It would be impossible for man a sinner to forgive another his sins if Christ had not first forgiven us, and second given us the authority and even the mandate to forgive that he does here.
Now someone is going to object. Here he is talking about trespasses against one’s self. He isn’t talking about forgiving someone for their sins against others or God. Listen sin is sin. In reality all sin is sin against you, all sin is sin against God. Some sins may affect you more directly and personally. But the world is so wired that one cannot sin against one’s neighbor without sinning also against you. And no one can sin without sinning against God. A sin against you is a sin against the God who both created you in his image, and redeemed that image with the sacrifice of his blood on the cross. This goes the other way too. When you sin against another you sin against God.
A man can go dizzy and into great despair contemplating sin, and just how massive a problem it is. No one has been forgiven more sin than you. That is the gist of this parable. So you too forgive. We have no right not to. Perhaps if we had not been forgiven ourselves we would have reason not to forgive, to hold a grudge. And in that case it would be impossible for us to forgive, sinful men that we are. But when Christ forgives us, he gives us the power, authority, reason, and mandate to forgive others too. And it is a joy to do so. To forgive is never something we do on our own, it is beyond our own ability, but it is something we do within the forgiveness of Christ, an extension of that forgiveness with which we have been forgiven. To say man can’t forgive, is really to say man has not been forgiven.