In these verses the apostle speaks very respectfully to the Corinthians, and with great skill; and, while he seems to excuse his urging them so earnestly to charity, still presses them thereto, and shows how much his heart was set upon this matter.
I. He tells them it was needless to press them with further arguments to afford relief to their poor brethren (Co2 9:1), being satisfied he had said enough already to prevail with those of whom he had so good an opinion. For, 1. He knew their forwardness to every good work, and how they had begun this good work a year ago, insomuch that, 2. He had boasted of their zeal to the Macedonians, and this had provoked many of them to do as they had done. Wherefore he was persuaded, that, as they had begun well, they would go on well; and so, commending them for what they had done, he lays an obligation on them to proceed and persevere.
II. He seems to apologize for sending Titus and the other brethren to them. He is unwilling they should be offended at him for this, as if he were too earnest, and pressed too hard upon them; and tells the true reasons why he sent them, namely, 1. That, having this timely notice, they might be fully ready (Co2 9:3), and not surprised with hasty demands, when he should come to them. When we would have others to do that which is good we must act towards them prudently and tenderly, and give them time. 2. That he might not be ashamed of his boasting concerning them, if they should be found unready, Co2 9:3, Co2 9:4. He intimates that some from Macedonia might haply come with him: and, if the collection should not then be made, this would make him, not to say them, ashamed, considering the boasting of the apostle concerning them. Thus careful was he to preserve their reputation and his own. Note, Christians should consult the reputation of their profession, and endeavour to adorn the doctrine of God our Saviour.

Yet have I sent the brethren - Titus and his companions, mentioned in the preceding chapter.
That, as I said, ye may be ready - And he wished them to be ready, that they might preserve the good character he had given them: this was for their honor; and if they did not take care to do so, he might be reputed a liar; and thus both they and himself be ashamed before the Macedonians, should any of them at this time accompany him to Corinth.

Yet have I sent the brethren,.... Titus, and the other two mentioned in the foregoing chapter: one manuscript reads, "we have sent"; and the Ethiopic version, "they have sent", that is, the Macedonians; but the common reading is best. It might be objected, that since the apostle knew the forwardness of their minds, how ready they were a year ago, and had boasted so much of their liberality, that it must be unnecessary to send the brethren to them, to stir them up to this work; which objection is prevented by observing the reason of his sending them:

lest our boasting of you should be in vain in this behalf: or, "in this part", in this particular thing, , "concerning this business", or affair of beneficence to the poor, as the Syriac version renders it. He had boasted of them with respect to other things besides this; but he was chiefly concerned, knowing the frailty and changeableness of human nature, and how possible it was that their forwardness might abate, and they grow cold and indifferent to such service, lest his glorying of them should be in vain in this particular instance; wherefore he sent the brethren to put them on, that as they had begun they would finish:

that as I said ye may be ready, That as he had said to the Macedonians, that they were ready in mind, it might appear to be so; or as he had ordered them in his former epistle, they might be actually ready; have their collection ready made, so that there might be no gathering when he came.

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-- (Co2 8:18, Co2 8:22) --Titus and the two others.

should be in vain in this behalf--"should be proved futile in this particular," however true in general (Co2 7:4). A tacit compliment, softening the sharp monition.

as I said--as I was saying (Co2 9:2).