Matthew 7:15-20

Beware of false prophets, which come to you in sheep's clothing, but inwardly are ravening wolves. By their fruits ye shall know them. Do men gather grapes of thorns, or figs of thistles? Even so every good tree bringeth forth good fruit; but the corrupt tree bringeth forth evil fruit. A good tree cannot bring forth evil fruit, neither can a corrupt tree bring forth good fruit. Every tree that bringeth not forth good fruit is hewn down, and cast into the fire. Therefore by their fruits ye shall know them.