Read or listen the Second Epistle to the Corinthians - chapter 13 online (ESV, Bible Gateway)

Even the weak can be strong – 2 Cor. 13:1-4

Paul prepares the Corinthian church for his third visit. Even on his previous visit – a short and unsuccessful visit from Ephesus – Paul had warned the sinners. What sins did he warn about? It has often been proposed that it was sexually related sins (cf. 1 Cor. 5:1), but it could have been about other sins too. In fact, it is not at all clear that it was only about one sin.

Paul had been called weak (2 Cor. 10:10). Now Paul points out that he can be strong when needed. Christ does not accept living in sin, and neither can Paul as an apostle of God. He had been patient, but now it was time to condemn sin so that the sinner would repent and be saved.

We too must be patient up to a certain limit. None of us is perfect, everyone falls. But it cannot justify the constant practice of sin.

The Corinthians had desired evidence that Christ was speaking through Paul (verse 3). Perhaps miracles and visions (cf. 2 Cor. 12:1-10) or speaking in tongues (1 Cor. 14:1-25) or other gifts of the Spirit were considered such evidence. However, Paul wanted to remain weak (2 Cor. 12:9-10) because then God could work through him. Christ was also weak when he was crucified, but his true power was revealed in his resurrection (verse 4).

This time Paul would also be strong in Corinth because the situation seemed to require it. Peter reminds us that God's judgement begins at the house of God, the church (1 Peter 4:17). Now, Paul was going to implement the judgement in the Corinthian church. In verse 1 Paul quotes Deuteronomy 19:15. There has been much speculation about the kind of judgement Paul was going to enforce. He might demand that the sinners be expelled from the church – that they either repent (cf. 1 Cor. 5:4) or, unrepentant, would go to eternal perdition.

Examine yourselves! – 2 Cor. 13:5-10

The Corinthians had been keen to criticize Paul. Now Paul is reminding them that the most important issue, however, is their own spiritual state. We too tend to evaluate the spirituality of others and at the same time we are inclined to forget our own spiritual state. God weighs everyone. We are all standing alone before our God.

This is not to say that we as Christians cannot rebuke others for sin (Matt. 18:15-18). If we were to wait for us to become perfect and only then would be willing to rebuke others, the rebuke would never take place.

Paul does not urge Corinthians – let alone Christians in later times – to continually examine themselves. He just wants to ask one, the most important, question: Do you belong to Christ? If you do not, you will not stand the test. The end of verse 5, then, is not about our feelings, but about what is our relationship with Christ.

Is Christ “in us” (e.g., ESV: Or do you not realize this about yourselves, that Jesus Christ is in you?) or “among you” (NLV: Surely you know that Jesus Christ is among you) (see also Col. 1:27)? Both translations are possible and there is support for both options elsewhere in the New Testament.
　The translation “Christ is among you” speaks of Christ living in the church. In Luke 17:20-21, Jesus speaks of the kingdom of God coming into the world in him, “among” (NLV) or “in the midst” (e.g., ESV) of men.
　“Christ in you” speaks of Christ dwelling in an individual Christian. This interpretation has been dear to many evangelical Christians in particular. Acts 17:27-29 and Galatians 2:20 can be used to support this interpretation.

"I have been crucified with Christ and I no longer live, but Christ lives in me. The life I now live in the body, I live by faith in the Son of God, who loved me and gave himself for me."
(Galatians 2:20)

If I had to choose between these two options here, I would choose "Christ in you," for Paul is talking about self-examination, that is, about individual Christians, not the whole church. Maybe Paul has had both options in mind. For both are true: Christ dwells in both individual Christians and the church.

In verse 7, Paul reminds the Corinthians that if they repent, he will not have to show his power and strength in Corinth. If he did it, somebody might blame Paul for unnecessary threatening (compare verses 1-4), but it does not bother Paul, because it is not about Paul's honour, but about God's will being done in Corinth (verse 8, cf. Rom. 9:3). The Corinthians’ repentance was also a prayer point for Paul (verse 9).

The passage reminds us that drifting away from the faith is possible. It may be that you go on your own way, away from Christ. Then you will not be able to stand at the final Judgement.

Concluding greetings – 2 Cor. 13:11-13

Once again, Paul pleads with the Corinthians to accept his exhortations. How did it work out for Paul? Was his letter understood and accepted or not? In Acts 20:2-3, Luke tells us that Paul’s third visit to Corinth lasted for three months. Such a long visit would probably not have been possible if the relationship between the Corinthian Christians and Paul had not been in order. The fact that this letter has been preserved for us also speaks in favour of the fact that the letter produced the result Paul desired.

The holy kiss (verse 12, see also 1 Cor. 16:20) is still a custom in some churches. It is associated with the celebration of Communion. In some churches it has been replaced by a handshake. The holy kiss was a sign of a deep bond. Jesus taught that we cannot have a true connection with God if our connection with other Christians is broken (Matt. 5:21-26).

“All the saints” (verse 13) refers to the church from which Paul sent his letter. Of the churches in Macedonia (2 Cor. 7:5-7), Philip is the most likely one. Verse 14 is also known as the Apostolic Blessing. The end of the verse can be translated as either "the fellowship of the Holy Spirit" (ESV) or "the communion of the Holy Spirit" (KJV).

It is often claimed that there is no doctrine of the Trinity in the Bible. But there are no other doctrines either, such as "the doctrine of Baptism" or "the doctrine of Communion". However, baptism, communion, and the Trinity do exist in the Bible. There are many passages in the New Testament where all the three persons of the Trinity are mentioned one after another, see for example: Matt. 28:18-20; Rom. 8:8-11, 15:16; 2 Cor. 1:21-22; Gal. 4:6; Eph. 2:18-22, 4:4-7; and Titus 3:4-7. Without faith in the Triune God, it would not have been possible to write like that.

The Trinity is regarded as the dividing line that determines whether a baptism is Christian. Baptism in the name of the Father and of the Son and of the Holy Spirit is Christian (cf. Matt. 28:18-20) and it is not renewed if a person moves from one Christian denomination to another. Other baptisms, however, are not Christian, and people who convert to Christianity from those religions are given a Christian baptism.

Paul mentions Christ as the first Person of the Trinity. Faith in Christ is the heart of Christianity. Grace is the fundamental Christian doctrine.

The Grace of Christ is the whole Christian faith summarised.