2 Corinthians 11:15

Therefore it is no great thing
It is no strange and wonderful thing; it may easily be given into; no man need to make any doubt of it, or hesitate concerning it, since the devil himself, who is an angel of darkness, is transformed into an angel of light:

if his ministers also be transformed as the ministers of
righteousness;
not that they really are transformed into such ministers, but they appear and look like such; they are not really, but "as the ministers of righteousness"; they put on the form and air of faithful upright ministers of the word, and would be thought to be such; they mimic Gospel preachers, who assert the doctrine of justification by the righteousness of Christ, though they most miserably corrupt it, and blend it with something of their own; and which they endeavour to palliate, and cover from the sight of men; and especially they set up themselves as such, by pretending to be great friends to holiness and good works, which they press with much vehemence, and oppose to the doctrines of grace, with all their might and main; in doing which, they greatly serve their master, whose ministers they are; and who well knows that the doctrine of works may do much prejudice to the Gospel interest, and churches of Christ, but will never convert nor save one soul: a dreadful character these men have, for though they would pass for ministers of righteousness, friends to holiness, and men zealous of good works, they are no other than ministers of Satan, doing his work, serving his interest, and propagating his kingdom, which is a kingdom of darkness:

whose end shall be according to their works;
for either God will make public examples of them in this world, or if they are not made manifest here, though they may deceive themselves and others, they cannot deceive God; he will take off the mask, their hypocrisy shall be detected, their evil works will be laid open, and they will be judged according to them, and condemned for them to everlasting punishment.