Pope St. Leo the Great ca. 400-461
[T]hough we are not anxious for vengeance, we cannot in any way be allied with the devil’s servants. Yet if we learn they are quitting the ranks of heresy, repenting them of their error and turning from the weapons of discord to the lamentations of sorrow, we also can intercede for them, lest they perish for ever, thus following the example of the Lord’s loving-kindness, who, when nailed to the wood of the cross prayed for His persecutors, Father, forgive them; for they know not what they do.” Lk. 23:34. That
Christian love may do this profitably for its enemies, wicked heretics must cease to harass God’s ever religious and ever devout Church; they must not dare to disturb the souls of the simple by their falsehoods, to the end that, where in all former times the purest faith has flourished, the teaching of the Gospel and of the Apostles may now also have free course; because we also imitating, so far as we can, the Divine mercy desire no one to be punished by justice, but all to be released by mercy. (Letter 164)
