When we hold a grudge against somebody, it prohibits us from fully forgiving them from whatever they've done to wrong us. While it's never easy for us to forgive others when they wrong us (especially when they don't ask to be forgiven), as Christians, it's something we have to do.
One of the greatest passages of scripture that teaches us a lesson on forgiveness is found in Matthew 18. Jesus talks in verses 21-35 about an unforgiving servant:
21Then 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?" 22Jesus said to him, "I do not say to you seven times, but seventy times seven.[a] 23"Therefore the kingdom of heaven may be compared to a king who wished to settle accounts with his servants.[b]24When he began to settle, one was brought to him who owed him ten thousand talents.[c] 25 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. 26So the servant[d] fell on his knees, imploring him, 'Have patience with me, and I will pay you everything.' 27And out of pity for him, the master of that servant released him and forgave him the debt. 28But when that same servant went out, he found one of his fellow servants who owed him a hundred denarii,[e] and seizing him, he began to choke him, saying, 'Pay what you owe.' 29So his fellow servant fell down and pleaded with him, 'Have patience with me, and I will pay you.' 30He refused and went and put him in prison until he should pay the debt. 31When 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. 32Then his master summoned him and said to him, 'You wicked servant! I forgave you all that debt because you pleaded with me. 33And should not you have had mercy on your fellow servant, as I had mercy on you?' 34 And in anger his master delivered him to the jailers,[f] until he should pay all his debt. 35 So also my heavenly Father will do to every one of you, if you do not forgive your brother from your heart."
This is a parable that I've read several times before but failed to notice something till just recently. I never thought twice about the "ten thousand talents" part of it. Ten thousand talents back then was basically an unfathomable sum of money. It would have been well over 100 years of work... just impossible to obtain. And it was immediately forgotten about by the master. While on the other hand, a hundred denarii would have been basically a day's work for a servant - yet the servant couldn't forgive his fellow worker and look beyond this. This is why this passage is so amazing. We do some horrible horrible things in our life - things that should have severe punishment - and we've done (and do) them time and time again. Yet, God is able to just throw them away - showing us the most amazing amount of grace and mercy. Yet, when others wrong us - even if its something small and trivial - we hold grudges and/or don't forgive them. When you read this parable it's so easy to say, "Wow, that guy's such a hypocrite for not forgiving the other servant!" - But we're just as guilty sometimes, are we not?
Forgiveness can be incredibly difficult at times. But if we're striving to be Christ-like in everything we say and do, we have to forgive all who sin against us.