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 (against you), your heavenly Father will not forgive your sins."
Luke 23:34, As Christ was being nailed to the cross He said, "Father, forgive them, for they do not know what they are doing."
Acts 7:60, At his stoning to death, Stephen cried out, "LORD, do not hold this sin against them." In the above words of Christ, "Father, forgive them."
To forgive such extreme sin, should make us realize forgiving others and asking others for forgiveness of sin to not have pride keep us from doing so.