Albert Barnes Commentary 2 Corinthians 13:9

"For we rejoice, when we are weak, and ye are strong: this we also pray for, even your perfecting." — 2 Corinthians 13:9 (ASV)

For we are glad, when we are weak, etc. We rejoice in your welfare and are willing to submit to self-denial and infirmity, if it may promote your spiritual strength.

In the connection in which this stands, it seems to mean: "I am content to appear weak, provided you do no wrong. I am willing not to have occasion to exercise my power in punishing offenders and would rather bear the reproach of being actually weak than to have occasion to exercise my power by punishing you for wrongdoing; and provided you are strong in the faith and in the hope of the gospel, I am very willing, nay, I rejoice that I am under this necessity of appearing weak."

And this also we wish. I desire this in addition to your doing no evil.

Even your perfection. The word used here occurs nowhere else in the New Testament, though the verb from which it is derived (katartizō) occurs often: Matthew 4:21; Matthew 21:16; Mark 1:19; Luke 6:40; Romans 9:22; 1 Corinthians 1:10; 2 Corinthians 13:11; Galatians 6:1; 1 Thessalonians 3:10, and elsewhere. See the notes on 2 Corinthians 13:11.

On the meaning of the word, see Romans 9:22. The idea of restoring, putting in order, fitting, repairing, is always involved in the word; and hence the idea of making perfect—that is, of completely restoring anything to its proper place. Here it evidently means that Paul wished their entire reformation—so that there should be no occasion for exercising discipline. Doddridge renders it, "perfect good order." Macknight, "restoration." For this restoration of good order Paul had diligently laboured in these epistles; and this was an object near to his heart.