Verses 12–13 fulfil three functions: 1) they confirm that the sinning brother of 1 Corinthians 5:1–5 is to be removed from the church; 2) they bring to a close Paul’s explanation of the command that he had given in his previous letter (1 Corinthians 5:9–11); 3) they serve as a bridge between the problem that was discussed in 1 Corinthians 5:1–13 and the problem that Paul will now turn to, namely, the settling of disputes within the church (1 Corinthians 6:1–8).
Once and for all, Paul clarifies that the church is to judge not those outside the church but those inside. The clear distinction between outsiders
and those inside
suggests that church membership was formally recognized by the New Testament church.
12 For what have I to do with judging outsiders? Is it not those inside the church whom you are to judge?