The simple believeth every word: but the prudent [man] looketh well to his going. Proverbs 14:15
Therefore hearken not ye to your prophets, nor to your diviners, nor to your dreamers, nor to your enchanters, nor to your sorcerers, which speak unto you, saying, Ye shall not serve the king of Babylon: For they prophesy a lie unto you, to remove you far from your land; and that I should drive you out, and ye should perish. Jeremiah 27:9-10
Beware of false prophets, which come to you in sheep's clothing, but inwardly they are ravening wolves. Ye shall know them by their fruits. Do men gather grapes of thorns, or figs of thistles? Matthew 7:15-16
Prove all things; hold fast that which is good. 1 Thessalonians 5:21