Again] probably refers to the passages in the severe letter (2 Corinthians 10-13) in which he defended himself and stated his claims to recognition: see especially 2 Corinthians 11:22-33; 2 Corinthians 12:1-5; 2 Corinthians 12:16-19.
As some] The Judaising leaders had probably brought letters from Palestine and charged St. Paul with having no such recommendations. Epistles of commendation] Such Epistles were commonly used in the early Church to introduce strangers; for examples see Romans 16 and Philemon, and cp. Acts 15:23-27; Acts 18:27.