7: Therefore, as ye abound in every thing, in faith, and utterance, and knowledge, and in all diligence, and in your love to us, see that ye abound in this grace also.

11: 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 ye have.

24: Wherefore show ye to them, and before the churches, the proof of your love, and of our boasting on your behalf.

The Corinthians excelled in many things concerning their Christianity—in faith, expression, knowledge, diligence and in love.  Now he’s telling them, or rather asking them to excel in their giving as well.  Giving is ‘this grace’ that he’s talking about.

But as he says in verse 8, he’s not dictating to them what to do but rather he’s pointing out other’s zeal, knowing that the Corinthians are sincere in their love and would want to excel in this area also.  In verse 11 he encourages them since they had begun to give to the relief of the saints in Jerusalem a year ago, and he encourages them to finish what they started and carry it out.

Again in verse 24 he says to show the proof of their love before the churches and the reason Paul had been boasting about them.

We should desire to be people that are zealous and excel in the work of the Lord in all areas.  Paul feels he is able to call on them to give for this cause because he knows their zeal and the sincere love they have in other areas.  He also knows they had already expressed an interest in giving before.  He had been boasting about their zeal for the Lord and wanted to see them prove that to others.