When Jesus taught the disciples how to pray in what has come to be known as the Lord’s Prayer, one of the points that he emphasized was forgiving “those who trespass against us.” Afterwards, he expounds on this:
Matthew 6:14-15
For if you forgive men when they sin against you, your heavenly Father will also forgive you. But if you do not forgive men their sins, your Father will not forgive your sins.
That sounds scary – the only way that we can be forgiven (and therefore saved) is if God forgives us of our sin, but he will not do that unless we forgive those who sin against us!