"Those who know God's mercy must operate on the principle of mercy. If they do not show mercy but insist on justice, they willl receive justice rather than mercy. We must not minimize the seriousness of this matter. An unforgiving heart is a heart that is subject to torment "until (its debtor) should pay back all" that is owed, which in the case of any human being equates to forever. A truly forgiving heart is the fruit of regeneration."
-Reformation of the Study Bible