TRANSLATION MATTHEW 7:15
Look out for pseudo- prophets, the ones who come to you dressed as sheep, but inside are ravenous wolves. You will recognise them from their fruits. Bunches of grapes are not gathered from briers, nor figs from thistles. Likewise, every sound tree bears good fruit, but the rotten tree bears bad fruit. The sound tree cannot bear bad fruit, or the rotten tree good fruit. Every tree that does not bear good fruit is cut down and thrown in the fire. So yes, you will recognise them by their fruits.
Again, we can note the robust language given to Jesus. I say “given” because of course someone has translated Jesus’ Aramaic into Greek, and Matthew has edited his source. But at least in the so-called synoptic gospels (Matthew, Mark, Luke) robust speech is a characteristic of Jesus, so we may guess it is authentic.
A community that has prophets will also have pseudo-prophets, looking for power, prestige or profit. Many of the great prophets of Israel were accused of being false, by people who didn’t like their message. Jesus makes no attempt to define a genuine message. Rather he focuses on their ‘fruits’ meaning their own actions and the results of their prophetic activity. If these are bad, they must proceed from bad people, for sound people will not produce badness in themselves or others.
This is a sane and liberating view of human character. Good actions and good communities are created by good people. Of course bad people may be disciplined to do the odd good thing, but for sustained goodness you have to look to good people. This means that any attempt to improve people must concentrate on the whole person; if they can grow into goodness, good actions will follow. No mere belief however orthodox or passionate can do this unless it enables genuine growth of character. Rabbi Jesus did not allow his followers to feel justified in the possession of clever interpretations of the Torah or the Prophets; he wanted them to become sound trees.