V12 "And forgive us our debts as we have forgiven our debtors."
The Bible has a lot to say about forgiveness. It says that forgiveness is from God. It says that sin must be forgiven an infinite amount of times (Matt 18: 21-22). It also says that God faithful to forgive us of all our sins (1 John 1:9). Even though we are unworthy, God bestows his love on us filling us with his own righteousness making us perfectly clean.
We, however, must forgive those who sin against us (Matthew 18: 21-35). To be clean in the eyes of the Father is an unfathomable gift that we must not squander. As part of showing g the Father's love, we must give love to others. An expression of that love is forgiveness. To withhold forgiveness is to deny someone love and to allow the root of bitterness to develop. Remaining bitter harms you more than them.
