פרשת שופטים - כִּ֤י הָֽאָדָם֙ עֵ֣ץ הַשָּׂדֶ֔ה

(19) When in your war against a city you have to besiege it a long time in order to capture it, you must not destroy its trees, wielding the ax against them. You may eat of them, but you must not cut them down. Are trees of the field human to withdraw before you into the besieged city? (20) Only trees that you know do not yield food may be destroyed; you may cut them down for constructing siegeworks against the city that is waging war on you, until it has been reduced.

Rabbi Yirmeya once said to Rabbi Zeira: Let the Master come and teach a halakhic discourse. Rabbi Zeira said to him: My heart is weak and I cannot strain myself over a halakhic discourse. Rabbi Yirmeya replied to him: In that case, let the Master tell us a matter of aggada, which does not require as much effort. Rabbi Zeira said to him that Rabbi Yoḥanan said as follows: What is the meaning of that which is written: “For man is a tree of the field” (Deuteronomy 20:19)? And is man actually a tree of the field? Rather, it is because it is written earlier in the same verse: “You may eat of them but you may not cut them down,” and it is written in the next verse: “Them you may destroy and cut down” (Deuteronomy 20:20). This indicates that there are certain trees which may be cut down, while others may not be destroyed. How so? If a Torah scholar is worthy: “You may eat of them but you may not cut them down,” but if he is not worthy: “He you may destroy and cut down.”

(220) "Does it have trees or not" (Numbers 13:20), as it is written in the Zohar "do not destroy its trees [etza] (Deut. 20:19) this is the student of the sages that advises [meyaetz] the people regarding teshuvah etc" (Zohar 3:202a and Zohar 3:202b). If so, in this case also, regarding an individual, the inclination to good is called tree, since it advises a person to Torah and teshuvah. And a person should test if the inclination to good rules them and advises them well, and if not, one should "exert yourselves and take", meaning that to do the opposite needs strength, and doing the opposite [of the yetzer hara] is "fruit of the land" since evil deeds are the husks and externals of the fruit, which does not happen regarding good deeds, which are the fruit themselves, and this is why is written "and exert yourselves and bring some of the fruit of the land".

Students increase their teacher's wisdom and broaden his horizons. Our Sages declared: "I learned much wisdom from my teachers and even more from my colleagues. However, from my students [I learned] most of all."Just as a small branch is used to light a large bough, so a small student sharpens his teacher's [thinking processes], until, through his questions, he brings forth brilliant wisdom.