Matthew 7:15
"Look out for false prophets, who come to you under the guise of sheep, but inside they are devouring wolves.
2 Corinthians 11:13-15
For such men are sham apostles, dishonest workmen, masquerading as apostles of Christ.
Galatians 1:8-9
But even if I or an angel from heaven preach a good news that is contrary to the one which I have already preached to you, a curse upon him!
1 John 4:1
Dearly beloved, stop believing every so-called spiritual utterance, but keep testing them to see whether they come from God, because many false prophets have gone out into the world.
Romans 1:21
because, although they once knew God, they did not honor Him as God, or give Him thanks, but became silly in their senseless speculations, and so their insensible hearts have been shrouded in darkness.