John Calvin Commentary 2 Corinthians 11:13

"For such men are false apostles, deceitful workers, fashioning themselves into apostles of Christ." — 2 Corinthians 11:13 (ASV)

For such are false Apostles—while he has already taken from them what they chiefly desired, yet, not content with having put himself on a level with them regarding what they were eager to excel in, he leaves them nothing for which they deserve any commendation. It was apparently a praiseworthy thing to despise money, but he says that they use a pretense to deceive, exactly as if a harlot were to borrow the attire of a decent matron. For it was necessary to pull off the mask, which obscured the glory of God.

They are deceitful workers, he says; that is—they do not reveal their wickedness at first sight but artfully insinuate themselves under some plausible pretext. Therefore, they require careful and thorough sifting, lest we receive people as servants of Christ as soon as any appearance of excellence is discovered. Nor does Paul, in malice and envy, interpret unfavorably what might be seen as an excellence; but, constrained by their dishonesty, he exposes the evil that lay hidden, because there was a dangerous profanation of virtue in their pretending to burn with greater zeal than all the servants of Christ.