Charles Ellicott Commentary 2 Corinthians 2:9

"For to this end also did I write, that I might know the proof of you, whether ye are obedient in all things." — 2 Corinthians 2:9 (ASV)

For to this end also did I write . . .—The tense of the Greek verb, which may be what is known as the Epistolary aorist (referring to the writer's perspective at the time of writing), would not be decisive as to what is referred to. The words may mean: “I write to you so to see whether you are as obedient now as you were before—in one line of action as in the other.”

If he refers to the First Epistle, it is to suggest that he gave the directions in 1 Corinthians 5:3–7 not only for the removal of a scandal and the reformation of the offender who had caused it, but also as a test of their obedience.

On the whole, the former interpretation seems preferable. It scarcely seems like St. Paul to make the punishment a trial of obedience. There is a characteristic subtle delicacy of thought in his suggesting that, having shown obedience in punishing, they should show it also in forgiving.