Read 2 Corinthians 13 at Bible Gateway.
A majority of this chapter forms an interesting chiastic structure:
2 Cor 13:1-10
1a) 2 Cor 13:1-3a, Paul’s authority in Christ:
— 1a.1) 2 Cor 13:1-2, Now being absent I write to those who have sinned, since when present I will not spare;
— 1a.2) 2 Cor 13:3a, Since you seek a proof of Christ speaking in me;
1b) 2 Cor 13:3b-4, Christ not weak toward you, but mighty in you /weak in Him, but shall live by the power of God;
1c) 2 Cor 13:5, Examine yourselves as to whether you are in the faith, that Jesus Christ is in you;
1d) 2 Cor 13:6, But I trust that you will know that we are not disqualified;
central axis) 2 Cor 13:7a, I pray that you do no evil / you should do what is honorable;
2d) 2 Cor 13:7b, Though we may seem disqualified;
2c) 2 Cor 13:8, For we can do nothing against the truth, but for the truth;
2b) 2 Cor 13:9, For we are glad when we are weak and you are strong;
2a) 2 Cor 13:10, Paul’s authority in Christ:
— 2a.1) 2 Cor 13:10a, Therefore I write these things being absent, lest being present I should use sharpness;
— 2a.2) 2 Cor 13:10b, According to the authority which the Lord has given me.
2 Corinthians 13:11
Paul says, Examine yourselves to see if you are really in the faith or not, if Jesus Christ is in you or not. Test yourselves. What is the test of faith?
Interestingly enough, earlier in this letter, Paul explained the difference between true and false ministers, and true and false apostles. The test in that case was the fruit of their ministry. Jesus said the same, that we will know who is true and false by their fruit (Mat 7:15-20). This is why the pair for Examine yourselves, is We can do nothing against the truth.
Truth reveals itself under examination. This is why witnesses are cross- examined on the witness stand. The process of examination shines a spotlight on truth and falsehood. Truth is confirmed under examination, and falsehood which has been masquerading as truth, is also revealed, the mask comes off.
So what is the test of faith? Fruit. The central axis highlights that those who are in the faith do no evil and do what is honorable (as a general lifestyle; he is not saying that those who are in the faith never commit a sin as an isolated incident). In other words, he is saying, Don’t be deceived, flock, because God is not deceived. If you are truly in the faith, then the fruit of your life will be the second witness along with the words of your mouth.