5. And forgive us our debts, as we forgive our debtors, This is connected with the former; and forgive, intimating, that unless our sins be pardoned, we can have no comfort in life, or the supports of it. Our daily bread does but feed us as lambs for the slaughter, if our sins be not pardoned. It intimates, likewise, that we must pray for daily pardon, as duly as we pray for daily bread. He that is washed, needeth to wash his feet. Here we have,
(1.) A petition; Father in heaven forgive us our debts, our debts to thee. Note, [1.] Our sins are our debts; there is a debt of duty, which, as creatures, we owe to our Creator; we do not pray to be discharged from that, but upon the non-payment of that there arises a debt of punishment; in default of obedience to the will of God, we become obnoxious to the wrath of God; and for not observing the precept of the law, we stand obliged to the penalty. A debtor is liable to process, so are we; a malefactor is a debtor to the law, so are we. [2.] Our hearts' desire and prayer to our heavenly Father every day should be, that he would forgive us our debts; that the obligation to punishment may be cancelled and vacated, that we may not come into condemnation; that we may be discharged, and have the comfort of it. In suing out the pardon of our sins, the great plea we have to rely upon is the satisfaction that was made to the justice of God for the sin of man, by the dying of the Lord Jesus our Surety, or rather Bail to the action, that undertook our discharge.
(2.) An argument to enforce this petition; as we forgive our debtors. This is not a plea of merit, but a plea of grace. Note, Those that come to God for the forgiveness of their sins against him, must make conscience of forgiving those who have offended them, else they curse themselves when they say the Lord's prayer. Our duty is to forgive our debtors; as to debts of money, we must not be rigorous and severe in exacting them from those that cannot pay them without ruining themselves and their families; but this means debt of injury; our debtors are those that trespass against us, that smite us (Mt 5:39,40), and in strictness of law, might be prosecuted for it; we must forbear, and forgive, and forget the affronts put upon us, and the wrongs done us; and this is a moral qualification for pardon and peace; it encourages to hope, that God will forgive us; for if there be in us this gracious disposition, it is wrought of God, and therefore is a perfection eminently and transcendently in himself; it will be an evidence to us that he has forgiven us, having wrought in us the condition of forgiveness.
Source: Matthew Henry's Commentary on the Whole Bible Volume V (Matthew to John)
Verse 12. And forgive us our debts, etc. The word debts is here used figuratively. It does not mean literally that we are debtors to God, but that our sins have a resemblance to debts. Debtors are those who are bound to others for some claim in commercial transactions; for something which we have had, and for which we are bound to pay according to contract. Literally, there can be no such transaction between God and us. It must be used figuratively. We have not met the claims of law; we have violated its obligations; we are exposed to its penalty; we are guilty; and God only can forgive, in the same way, as none but a creditor can forgive a debtor. Debts here, therefore, mean sins, or offences against God-- offences which none but God can forgive. The measure by which we may expect forgiveness is that which we use in reference to others. See Ps 18:25,26, Mt 18:28-35, Mk 11:25, Lk 11:4. This is the invariable rule by which God dispenses pardon. He that comes before him unwilling to forgive, harbouring dark and revengeful thoughts, how can he expect that God will show him that mercy which he is unwilling to show to others? It is not, however, required that we should forgive debts in a pecuniary sense. To them we have a right, though they should not be pushed with an overbearing and oppressive spirit; not so as to sacrifice the feelings of mercy, in order to secure the claims of right. No man has a right to oppress; and when a debt cannot be paid, or when it would greatly distress a wife and children, a widow and an orphan, or when calamity has put it out of the power of an honest man to pay the debt, the spirit of Christianity requires that it should be forgiven. To such cases this petition in the Lord's prayer doubtless extends. But it was probably intended to refer principally to injuries of character or person, which we have received from others. If we cannot from the heart forgive them, we have the assurance that God will never forgive us.
(z) "forgive us our debts" Mt 18:21-35, Lk 7:40-48
Source: Barnes' New Testament Notes