Q. 126. Which is the fifth petition?
“And forgive us our debts, as we forgive our debtors”; that is, be pleased for the sake of Christ’s blood, not to impute to us poor sinners, our transgressions, nor that depravity, which always cleaves to us; even as we feel this evidence of thy grace in us, that it is our firm resolution from the heart to forgive our neighbour.
 Matthew 6:12;  Psalm 51:1; 1 John 2:1–2;  Matthew 6:14–15.
“And forgive us our debts as we forgive our debtors.” That is: Be pleased, for the sake of Christ’s blood, not to impute to us, miserable sinners, our manifold transgressions, nor the evil which still always cleaves to us, as we find this witness of Thy grace in us, that it is our full purpose heartily to forgive our neighbour.
There are really two parts in this petition, though it is intricately tied. The first part is a plea to God to forgive us our debts against God or, in other words, our sins. But have not all our sins already been paid for and forgiven in Christ’s one perfect sacrifice (Heb 9:28; 10:12; Col 1:14)? Why then does the Lord teach us to ask for forgiveness?
First of all, God’s forgiveness of our sin is not a mere abstract intellectual notion. All whom He forgives will confess their sins, and it is those who would confess their sins that He forgives: “If we say that we have no sin, we deceive ourselves, and the truth is not in us. If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness” (1 Jn 1:8–9). Anyone who thinks he is forgiven and therefore does not think it necessary to confess his sins cannot possibly have experienced forgiveness.
Secondly, though our sins have been paid for, so that we are no longer subject to God’s wrath and condemnation, we are yet subject to His fatherly displeasure when we sin. Thus the Psalmist acknowledges that God will not hear one who is entertaining known, unrepented sins in his heart: “If I regard iniquity in my heart, the Lord will not hear me” (Ps 66:18); and he speaks of how guilt weighs him down: “When I kept silence, my bones waxed old through my roaring all the day long. For day and night thy hand was heavy upon me: my moisture is turned into the drought of summer” (Ps 32:3–4).
We must therefore come before the Lord, daily, to confess our sins. We should do so that God will, for Christ’s sake, turn His fatherly displeasure from us, that we may again enjoy the joy of His salvation (Ps 51:12) and the blessedness of forgiveness (Ps 32:1–5). Unrepentance on our part will not only make or cause us to loose our joy of fellowship with God, but may render us liable for chastisement by the Lord.
The second part of this petition is not really a petition, but an acknowledgment that we understand what it means to be forgiven: “as we forgive our debtors.” One who understands how greatly he has been forgiven by God, or how great a price it was by which God forgives us, will forgive others for their little debts against us. Are these debts not insignificantly small compared to our debt to our Master? Remember the Parable of the Unforgiving Steward (Mt 18:23–35). No one who evidences an unforgiving spirit can claim to have been forgiven by God, without mocking God, for that unforgiving spirit itself is a grievous sin, which needs first to be repented of.
Heidelberg Catechism >