DEUT1013 R. Yochanan said: "For a man is a tree of the field" -- Now is a man a tree of the field! But [understand it thus:] it is written; "for from it shall you eat, but it shall you not cut down"; and (verse 20): "it shall you destroy and cut down." How is this to be resolved? [Midrashically,]: If he [i.e., one who would be your teacher] is a genuine Torah scholar, "from him shall you eat, and him shall you not cut down"; if not, "him shall you destroy and cut down" (Ta'anith 7a)
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