Albert Barnes on 2 Corinthians 13:1

This is the third time, etc. 12:4. For an interesting view of this passage, see Paley's Horae Paulinae on this epistle, No. xi. It is evident that Paul had been to Corinth but once before this, but he had resolved to go before a second time, but had been disappointed.

In the mouth of two or three witnesses, etc. This was what the law of Moses required, De 19:15. Jn 8:17. Comp. Mt 18:16. But in regard to its application here, commentators are not agreed. Some suppose that Paul refers to his own epistles which he had sent to them as the two or three witnesses by which his promise to them would be made certain; that he had purposed it and promised it two or three times; and that as this was all that was required by the law, it would certainly be established. This is the opinion of Bloomfield, Rosenmuller, Grotius, Hammond, Locke, and some others. But, with all the respect due to such great names, it seems to me that this would be trifling and childish in the extreme. Lightfoot supposes that he refers to Stephanas, Fortunatus, and Achaicus, who would be witnesses to them of his purpose. See 1Cor 16:17. But the more probable opinion, it seems to me, is that of Doddridge, Macknight, and others, that he anticipated that there would be necessity for the administration of discipline there, but that he would feel himself under obligation in administering it to adhere to the reasonable maxim of the Jewish law. No one should be condemned or punished where there were not at least two or three witnesses to prove the offence; but where there were, discipline would be administered,according to the nature of the crime.

(d) "In the mouth" De 19:15, Heb 10:28,29