John Calvin Commentary 2 Corinthians 9:14

"while they themselves also, with supplication on your behalf, long after you by reason of the exceeding grace of God in you." — 2 Corinthians 9:14 (ASV)

And their prayer He omits no advantage that may be useful for stirring up the Corinthians. In the first place, he has mentioned the comfort that believers would experience; secondly, the thanksgiving, by which God was to be glorified.

Moreover, he has said that this would be a confession, which would manifest to all their unanimous agreement in faith and in pious obedience. He now adds the reward that the Corinthians would receive from the saints — goodwill springing from gratitude, and earnest prayers.

“They will have,” he says, “the means of repaying you; for they will regard you with the love as they ought, and they will be careful to commend you to God in their prayers.” Finally, as though he had obtained his desire, he prepares himself to celebrate the praises of God, by which he desired to testify his confidence, as though the matter were already accomplished.