8 Our Lord Jesus Christ, in teaching us how to pray to God, makes us say that we wish for pardon as we forgive others: "Forgive us our trespasses as we forgive them that trespass against Us." And if the observance of this law is sometimes hard and difficult, we have not only the timely assistance of the grace of Our Divine Redeemer, but also His example to help us to overcome the difficulty. For as He hung on the Cross He thus excused before his Father those who so unjustly and wickedly tortured Him: "Father, forgive them, for they know not what they do." We then, who should be the first to imitate the piety and loving kindness of Jesus Christ, whose Vicar, without any merit of Our own, We are; with all Our heart, and following His example, We forgive all Our enemies who knowingly or unknowingly have heaped and are still heaping on our person and Our work every sort of vituperation, and We embrace all in Our charity and benevolence, and neglect no opportunity to do them all the good in Our power. That is indeed what Christians worthy of the name ought to do towards those who during the war have done them wrong.
Source: Pacem, Dei Munus Pulcherrimum (Vatican.va)