Matthew 7:20
Thus you will recognize them by their fruits. The repetition of the fruit-recognition principle from verse 16 frames the diseased-tree teaching as a unit. The thus-you-will-recognize-them is the confident assertion that the diagnostic works: false prophets will be identifiable to those who pay attention over time. The Sermon's ethic of fruit-examination applies first to the disciple's own life (log-and-speck) and then to the evaluation of teachers and leaders (sheep's clothing and ravenous wolves). Both applications require sustained attention and the courage to act on what the examination reveals.