3. have I sent—we should say, "I send"; whereas the ancients put it in the past, the time which it would be by the time that the letter arrived.
the brethren—(2Co 8:18, 22)—Titus and the two others.
should be in vain in this behalf—"should be proved futile in this particular," however true in general (2Co 7:4). A tacit compliment, softening the sharp monition.
as I said—as I was saying (2Co 9:2).