John Wesley on Matthew 7:16

By their fruits ye shall know them - A short, plain, easy rule, whereby to know true from false prophets: and one that may be applied by people of the weakest capacity, who are not accustomed to deep reasoning. True prophets convert sinners to God, or at least confirm and strengthen those that are converted. False prophets do not. They also are false prophets, who though speaking the very truth, yet are not sent by the Spirit of God, but come in their own name, to declare it: their grand mark is, "Not turning men from the power of Satan to God." Luke 6:43,44.