That when we have received a wrong, we must remit and forgive it
In the Gospel, in the daily prayer: “Forgive us our debts, even as we forgive our debtors.” Also according to Mark: “And when you stand for prayer, forgive, if you have ought against any one; that also your Father who is in heaven may forgive you your sins. But if you do not forgive, neither will your Father which is in heaven forgive you your sins.” Also in the same place: “In what measure you mete, in that shall it be measured to you again.”
Source: The Treatises of Cyprian (New Advent)