Jamieson, Fausset and Brown on 2 Corinthians 8:14

14. by an equality--"by the rule of equality" [Alford]: literally, "Out of equality."

now at this time--Greek, "at the present juncture" or season.

that their abundance also--The Greek being distinct from the previous "that," translate, "in order that," namely, at another season, when your relative circumstances may be reversed. The reference is solely to temporal wants and supplies. Those, as Bengel, who quote Ro 15:27 for interpreting it of spiritual supplies from the Jews to the Gentiles, forget that Ro 15:27 refers to the past benefit spiritually, which the Jews have conferred on the Gentiles, as a motive to gratitude on the part of the latter, not to a prospective benefit to be looked for from the former, which the text refers to.