Jamieson, Fausset and Brown on 2 Corinthians 9:13

13. by--through occasion of.

experiment--Translate, "the experience" [Ellicott and others]. Or, "the experimental proof" of your Christian character, afforded by "this ministration."

they--the recipients.

for your professed subjection--Greek, "for the subjection of your profession"; that is, your subjection in accordance with your profession, in relation to the Gospel. Ye yield yourselves in willing subjection to the Gospel precepts, evinced in acts, as well as in profession.

your liberal distribution--Greek, "the liberality of your contribution in relation to them," &c.