Matthew 7:15
Beware of false Teachers--men who come to you in the guise of sheep, but at heart they are ravenous wolves.
2 Corinthians 11:13-15
Men of this stamp are false apostles, treacherous workers, disguising themselves as Apostles of Christ!
Galatians 1:8-9
Yet even if we--or if an angel from Heaven were to tell you any other 'Good News' than that which we told you, may he be accursed!
1 John 4:1
Dear friends, do not trust every inspiration, but test each inspiration, to see whether it proceeds from God; because many false Prophets have gone out into the world.
Romans 1:21
Because, although they learned to know God, yet they did not offer him as God either praise or thanksgiving. Their speculations about him proved futile, and their undiscerning minds were darkened.