If the fire of the Sun of Righteousness has touched our souls, it will leave nothing frozen, nothing hard, nothing burning, nothing unfruitful. It will bring out all things ripe, all things sweet, all things abounding with much pleasure. If we love one another, that beam also will come. Allow me, I beseech you, to say these things with earnestness. Cause me to hear, that by these words we have produced some effect; that some one has gone and thrown both his arms about his enemy, has embraced him, has twined himself around him, has warmly kissed him, has wept.
And though the other be a wild beast, a stone, or whatever he be, he will be made gentle by such affectionate kindness. For on what account is he your enemy? Hath he insulted you? Yet he has not injured you at all. But do you for the sake of money suffer your brother to be at enmity with you? Do not so, I beseech you. Let us do away all. It is our season. Let us use it to good purpose. Let us cut asunder the cords of our sins. Before we go away to judgment, let us not ourselves judge one another.
“Let not the sun” (it is said) “go down upon your wrath.” Let no one put it off. These puttings off produce delays. If you have deferred it today, you blush the more, and if you add tomorrow, the shame is greater, and if a third day, yet worse. Let us not then put ourselves to shame, but let us forgive, that we may be forgiven. And if we be forgiven, we shall obtain all blessings, through Jesus Christ our Lord, with whom, etc.
Source: Homilies on First Thessalonians (New Advent)