Why did Paul want the Corinthians to give before he arrived?
He wanted the Corinthians to set aside their gift before he arrived so their giving would not be swayed by his presence. He did not want them to give merely to impress him or to respond to his influence, but to give freely as God had prospered them.
Les teaches that Christian giving is beautiful because it rests on grace and free will, not on a mandatory set amount. The ten percent figure is a guideline, but under Paul's teaching believers are not commanded to give a specific percentage. Paul therefore wanted the collection completed before he got there so the Corinthians would not be under his influence. He did not want them digging into another pocket just because Paul was present and would see how much they gave. He wanted their giving to be voluntary, as God had prospered them, rather than done to impress him.