Now therefore perform the doing of it; that as there was a readiness to will, so there may be a performance also out of that which you have.
Read Chapter 8
Paul is saying that the Corinthians should give as much as they are willing and able to give. That way their conscience would become clear and not be clouded by pretense, pleasing man but not God. Commentary on Paul’s Epistles.
So there may be a performance. Lucian"s lines are well known:—
"Sweeter is grace that is prompt;
If slow is the hand that bestows,
Its grace becomes empty and vain
And title to grace must resign."
"He double gives who promptly gives."
And now also you have completed the doing of it.
He said not, you have done it, but, you have put a completion to it,
That as there was the readiness to will, so also [there may be] the completion also out of your ability.
That this good work halt not at readiness but receive also the reward that follows upon deeds.