I speak not by commandment, but by occasion of the forwardness of others, and to prove the sincerity of your love. I speak not by commandment - I do not positively order this; I assume no right or authority over your property; what you devote of your substance to charitable purposes must be your own work, and a free-will offering.
The forwardness of others - Viz. the Churches of Macedonia, which had already exerted themselves so very much in this good work. And the apostle here intimates that he takes this opportunity to apprise them of the zeal of the Macedonians, lest those at Corinth, who excelled in every other gift, should be outdone in this. Their own honor, if better motives were absent, would induce them to exert themselves, that they might not be outdone by others. And then, as they had professed great love for the apostle, and this was a service that lay near his heart, they would prove the sincerity of that professed love by a liberal contribution for the afflicted and destitute Jewish Christians.