Forgive that you may be forgiven (CLEMENT OF ROME).
If we entreat the Lord to forgive us, we ought also ourselves to forgive (POLYCARP).
Let no one cherish any grudge against his neighbor (IGNATIUS).
The Lord will deliver over to death all those whom He shall find retaining a recollection of offenses (HERMAS).
It is in the power of God alone to grant the forgiveness of sins, since also the Lord commands us each day to forgive the repenting brethren (CLEMENT OF ALEXANDRIA).
What sort of deed is it to approach the peace of God without peace or the remission of debts while you retain them? (TERTULLIAN).
We should ask that our debts be forgiven us in such a manner as we ourselves forgive our debtors (CYPRIAN).
Even as you desire that He may remit your transgressions, also forgive them theirs (THEONAS OF ALEXANDRIA).
See also commentary above on Matthew 6:12.