The following is from St. Aelred of Rievaulx's Speculum Caritatis,"The Mirror of Love," as excerpted for today's Office of Readings in the Breviary:
Who could listen to that wonderful prayer, so full of warmth, of love, of unshakable serenity--"Father, forgive them"--and hesitate to embrace his enemies with overflowing love? "Father," he says, "forgive them." Is any gentleness, any love, lacking in this prayer?
Yet he put into it something more. It was not enough to pray for them: he wanted also to make excuses for them. "Father, forgive them, for they know not what they are doing." They are great sinners, yes, but they have little judgment; therefore, "Father, forgive them." They are nailing me to the cross, but they do not know who it is that they are nailing to the cross: "if they had known, they would never have crucified the Lord of glory [I Corinthians 2:8]"; therfore, "Father, forgive them." They think it is a lawbreaker, an imposter claiming to be God, a seducer of the people. I have hidden my face from them, and they do not recognize my glory: therefore, "Father, forgive them, for they do not know what they are doing."
For myself, it is very hard not to be deeply moved by this passage...