2 Corinthians 13:10
For this cause I write these things while absent, that I may not when present deal sharply, according to the authority which the Lord gave me for building up, and not for casting down.
He was sensible he had spoken more vehemently than his wont, and especially towards the end of the Epistle. For he said before, “Now I Paul myself entreat you by the meekness and gentleness of Christ; I who in your presence am lowly among you, but being absent am of good courage towards you: Yea, I beseech you, that I may not be bold when I am present, with the confidence wherewith I count to be bold against some which count of us as if we walked according to the flesh;” and, “being in readiness to avenge all disobedience when your obedience shall be fulfilled:” and, “I fear lest when I come, I should find you not such as I would, and should myself be found of you such as you would not;” and again, “lest when I come my God should humble me before you, and that I should mourn many of them which have sinned heretofore, and repented not of the lasciviousness and uncleanness which they committed:” and afterwards, “I told you before and foretell you, as if I were present the second time, and being absent now I write, that, if I come again, I will not spare; seeing that you seek a proof of Christ, that speaks in me.” Since then he had said these things and more besides, terrifying, shaming, reproaching, lashing them, he says, in excuse for all, “For this cause I write these things while absent, that I may not when present deal sharply.” For I am desirous the sharpness should lie in my letters and not in my deeds. I wish my threats to be vehement, that they may continue threats and never go forth into action. Again even in this his apology he makes what he says more terrible, showing that it is not himself who is to punish, but God; for he added, “according to the authority which the Lord gave me;” and again, to show that he desires not to use his power to their punishment, he added, “not for casting down, but for building up.” And he hinted indeed this now, as I said, but he left it to them to draw the conclusion that if they should continue unamended, even this again is building up, to punish those that are of such a mind. For so it is, and he knew it and showed it by his deeds.
Source: Homilies on Second Corinthians (New Advent)