Matthew 7:15-20

Beware of false prophets, who come to you dressed as sheep, but inside they are devouring wolves. [Ezek. 22:27.] You will fully recognize them by their fruits. Do people pick grapes from thorns, or figs from thistles? Even so, every healthy (sound) tree bears good fruit [worthy of admiration], but the sickly (decaying, worthless) tree bears bad (worthless) fruit. A good (healthy) tree cannot bear bad (worthless) fruit, nor can a bad (diseased) tree bear excellent fruit [worthy of admiration]. Every tree that does not bear good fruit is cut down and cast into the fire. Therefore, you will fully know them by their fruits.