Jesus’ teaching on binding and loosing is a bit perplexing and worthy of careful contemplation. A parallel passage talks about forgiving sin and is even more disconcerting.
Jesus says that if we forgive someone’s sins, they will be forgiven; conversely if we don’t forgive someone’s sins, they will not be forgiven.
That is an even heavier burden, realizing that our holding of a grudge — that is, not forgiving someone — will result in the withholding of forgiveness for their sins.
However, it is even more weighty than that.
Consider the “Lord’s Prayer” and the phrase “forgive us our sins as we forgive those who sin against us.” Through this prayer we are actually asking God to only forgive us to the degree to which we forgive others.
Given the severity of the ramifications, we need to be most diligent in forgiving all others and not holding a grudge.