Charles Ellicott Commentary 2 Corinthians 8:5

"and [this], not as we had hoped, but first they gave their own selves to the Lord, and to us through the will of God." — 2 Corinthians 8:5 (ASV)

Not as we hoped . . .—This means, of course, that they had done what was far beyond his hopes; and here the point lies in the fact that they gave, not their money only, but themselves, their time, thought, energy, primarily to Christ as their Lord, and then to the Apostle as His minister. And this they had done because they allowed the will of God to work upon their will.