John Chrysostom

"That being enriched in every thing to all liberality, which worketh through us thanksgiving to God." Not that ye may consume it upon things not fitting, but upon such as bring much thanksgiving to God. For God made us to have the disposal of great things, and reserving to Himself that which is less yielded to us that which is greater. For corporeal nourishment is at His sole disposal, but mental He permitted to us; for we have it at our own disposal whether the crops we have to show be luxuriant. …

Homily 20 on 2 Corinthians ↗

Theophylact of Ohrid

Again he shows how one should use wealth, and says that one should not bury it in the ground, but have it "for all generosity," that is, share it generously. But since many find generosity in harlots and actors, he says: I mean that generosity which brings "thanksgiving" to God, and not only thanksgiving, but many other things, which he speaks of further, so that by showing the many good consequences of generosity, he might make them more zealous for it.

Commentary on 2 Corinthians ↗

Thomas Aquinas

Then when he says, You will be enriched in every way, after having assigned the reason why they should give promptly, abundantly and cheerfully on the part of the donors, he then assigns the reason on God's part, for whom they ought to give. First he assigns the reason they should give; secondly, he explains it (v. 12). In the reason to be assigned, three things are to be considered, the first of which is their enrichment, which corresponds to what has gone above. …

Commentary on 2 Corinthians ↗