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.

It is superfluous for me to write to you - I need not enlarge, having already said enough. See the preceding chapter, (2 Corinthians 8 (note)).

For as touching the ministering to the saints,.... It looks at first sight as if the apostle was entering upon a new subject, though by what follows it appears to be the same; for by "ministering to the saints", he does not mean the ministry of the Gospel to them; nor that mutual assistance members of churches are to give each other; but either the fellowship of ministering to the saints, which the churches had entreated him, and his fellow ministers, to take upon them, namely, to take the charge of their collections, and distribute them to the poor saints at Jerusalem; or rather these collections themselves, and their liberality in them: with respect to which he says,

it is superfluous for me to write to you; that is, he thought it unnecessary to say any more upon that head, because he had used so many arguments already to engage them in it, in the foregoing chapter; and because he had sent three brethren to them, who well understood the nature of this service, and were very capable of speaking to it, and of enforcing the reasonings already used; and more especially he judged it needless to dwell on this subject, for the reasons following.