Adam Clarke on 2 Corinthians 12:16

But be it so, I did not burden you - That is: You grant that I did not burden you, that I took nothing from you, but preached to you the Gospel freely; but you say that, Being Crafty, I caught you with guile; i.e. getting from you, by means of others, what I pretended to be unwilling to receive immediately from yourselves.

Many persons suppose that the words, being crafty, I caught you with guile, are the words of the apostle and not of his slanderers; and therefore have concluded that it is lawful to use guile, deceit, etc., in order to serve a good and a religious purpose. This doctrine is abominable; and the words are most evidently those of the apostle's detractors, against which he defends his conduct in the two following verses.