I am glad of the coming - That is, I am glad that they have come to me at Ephesus. I rejoice that he who was converted by my ministry in Achaia, and who has so long shown himself to be a personal friend to me, and an aid in my work, came where I am.
Stephanas - The same person evidently mentioned in the previous verses. Probably he, as one of the oldest and most respected members of the church, had been selected to carry the letter of the Corinthians 1 Corinthians 7:1 to Paul, and to consult with him respecting the affairs of the church there.
Fortunatus and Achaieus - These persons are not referred to anywhere else in the New Testament. It appears that Fortunatus survived Paul, for he was subsequently the messenger of the church at Corinth to that at Rome, and bore back to the Corinthians the Epistle which Clement of Rome sent to them. See that epistle, Section 59.
For that which was lacking ... - The word which is used here, and rendered “that which was lacking” (ὑστέρημα husterēma), does not occur in the Classic writers. It means properly that which is missing, want, lack - Robinson. It may be used to denote a want or lack of any kind, whether of support, sustenance, aid, consolation, information, or counsel; see Luke 21:4; Philippians 2:30; 1 Thessalonians 3:10. What this was which the Corinthians had neglected or failed to furnish Paul, and which had been supplied by the presence of these persons, can be only a matter of conjecture; and different commentators have supposed different things. It might be a neglect to provide for his needs, or a defect of informing him about their affairs in the letter which they had sent him; or it might be that these persons had furnished, by their presence and conversation, those consolations and friendly offices which the church at Corinth would have rendered had they been all present; and Paul may mean to say, that he had enjoyed with them that friendly contact and Christian communion which he had desired with them, but which was lacking, that is, which he had not been permitted to enjoy by reason of his absence. This is the view which is given by Rosenmuller, Doddridge, Bloomfield; and as Paul does not seem here inclined to blame them, this view is most in accordance with the general strain of the passage.