When you ought to tremble for your own sins, to wrestle earnestly for the pardon of them, you come to move God against your brother— do you not fear, nor think of what concerns yourself? Do you not see what you are doing? Imitate even the conduct of children at school. If they see their own class within giving account of their lessons, and all beaten for their idleness, and one by one severely examined and chastised with blows, they are frightened to death, and if one of their companions strikes them, and that severely, they cannot have while to be angry, nor complain to their master; so is their soul possessed with fear.
They only look to one thing, that they may go in and come out without stripes, and their thoughts are on that time. And when they come out, whether beaten or not, the blows they have received from their playmates never enter their minds for the delight. And you, when you stand anxiously concerned for your own sins, how can you but shudder at making mention of others' faults? How can you implore pardon of God? For your own case is made worse on the terms of your imprecations against another, and you forbid Him to make allowance for your own faults.
Might He not say, “If you would have Me so severe in exacting offenses against you, how can you expect Me to pardon your offenses against Me?” Let us learn at last to be Christians! If we know not how to pray, which is a very simple and easy thing, what else shall we know? Let us learn to pray like Christians. Those are the prayers of Gentiles, the supplications of Jews. The Christian's are the reverse, for the forgiveness and forgetting of offenses against us. “Being reviled,” it is said, “we bless; being persecuted, we suffer it; being defamed, we entreat.” Hear Stephen saying, “Lord, lay not this sin to their charge.” Instead of praying against them, he prayed for them.
You, instead of praying for them, utter imprecations against them. You then are wicked in the degree that he was excellent. Whom do we admire, tell me; those for whom he prayed, or him who prayed for them? Him certainly! And if we, much more then God. Would you have your enemy stricken? pray for him: yet not with such intention, not to strike him. That will indeed be the effect, but let it not be your object. That blessed martyr suffered all unjustly, yet he prayed for them: we suffer many things justly from our enemies.
And if he who suffered unjustly dared not forbear to pray for his enemies, what punishment do we deserve, who suffer justly, and yet do not pray for them, nay, pray against them? You think indeed that you are inflicting a blow upon another, but in truth you are thrusting the sword against yourself. You allow not the Judge to be lenient to your own offenses, by this way of urging Him to anger against others. For, “with what measure you mete,” He says, “it shall be measured to you again; and with what judgment you judge, you shall be judged.” Let us therefore be disposed to pardon, that God may be so disposed towards us.
Source: Homilies on First Timothy (New Advent)