13
I will not spare
This is the third time I am coming to you. “At the mouth of two or three witnesses shall every word be established.”* See Deuteronomy 19:15. It almost seems that Paul is comparing his visits to witnesses. As I already said while with you the second time, I now repeat in writing Perhaps 3% of the Greek manuscripts omit “in writing”, to be followed by NIV, NASB, LB, TEV, etc. while absent, to those who sinned before and to all the rest: If I come again I will not spare, since you want proof that Christ is speaking through me—He who is not weak toward you but powerful among you (although He was crucified in weakness, He lives by the power of God). Now we also are weak in Him, but we will live with Him by the power of God toward you. Being weak in God's presence is one thing; being weak in our work for Him is quite another. I take Paul to be saying that being weak in God's presence triggers the outflow of His power in our work.
Examine yourselves
Examine yourselves as to whether you are in the faith; test yourselves. Do you yourselves really not know that Jesus Christ is in you?§ Sin does have a way of undermining confidence. A Christian who keeps on sinning tends to become less and less sure of his salvation.—unless indeed you are disqualified. Well I trust that you will know that we are not disqualified.
Now I pray to God that you do no evil; not that we may appear approved, but that you may do what is right (even though we may appear to have failed).* I don't understand this. For we cannot do anything against the Truth, but only for the Truth. Now we are glad when we are weak and you are strong. And we also pray for this, your perfecting. 10 This is why I write these things while absent, so that when present I may not have to deal harshly, according to the authority that the Lord gave me, for building up and not for tearing down.
Conclusion
11 Finally, brothers, rejoice; restore each other; encourage one another; be of one mind; live in peace; and the God of the love and the peace will be with you.
12 Greet one another with a holy kiss.
13 All the saints greet you.
14 The grace of our Lord Jesus Christ, and the love of God, and the fellowship of the Holy Spirit be with you all. Here we have a clear reference to the Trinity.
Amen.

*13:1 See Deuteronomy 19:15. It almost seems that Paul is comparing his visits to witnesses.

13:2 Perhaps 3% of the Greek manuscripts omit “in writing”, to be followed by NIV, NASB, LB, TEV, etc.

13:4 Being weak in God's presence is one thing; being weak in our work for Him is quite another. I take Paul to be saying that being weak in God's presence triggers the outflow of His power in our work.

§13:5 Sin does have a way of undermining confidence. A Christian who keeps on sinning tends to become less and less sure of his salvation.

*13:7 I don't understand this.

13:14 Here we have a clear reference to the Trinity.