Taanit 7a:1
Rav Nachman bar Yitzchak said: Why was the Torah compared to a tree, as it says "for it is a tree of life for those who hold fast to it" (Proverbs 3:18)? To teach you that just as a small tree may set a larger tree on fire, so too is it with scholars, where the small sharpen the large. After all, Rabbi Chanania said "I have learnt much from my teachers, and more from my friends, but from my students more than anyone"
(ח) וְהָיָ֞ה כְּעֵ֣ץ ׀ שָׁת֣וּל עַל־מַ֗יִם וְעַל־יוּבַל֙ יְשַׁלַּ֣ח שָֽׁרָשָׁ֔יו וְלֹ֤א ירא [יִרְאֶה֙] כִּֽי־יָבֹ֣א חֹ֔ם וְהָיָ֥ה עָלֵ֖הוּ רַֽעֲנָ֑ן וּבִשְׁנַ֤ת בַּצֹּ֙רֶת֙ לֹ֣א יִדְאָ֔ג וְלֹ֥א יָמִ֖ישׁ מֵעֲשׂ֥וֹת פֶּֽרִי׃
(8) For he shall be as a tree planted by the waters, And that spreadeth out its roots by the river, And shall not see when heat cometh, But its foliage shall be luxuriant; And shall not be anxious in the year of drought, Neither shall cease from yielding fruit.
Taanit 5b
When they were about to part, [R. Nahman] said: Please, Rabbi, bless me. He replied: Let me tell you a parable — To what may this be compared? To a man who was journeying in the desert; he was hungry, weary and thirsty and he lighted upon a tree the fruits of which were sweet, its shade pleasant, and a stream of water flowing beneath it; he ate of its fruits, drank of the water, and rested under its shade. When he was about to continue his journey, he said: Tree, O Tree, with what shall I bless you? Shall I say to you, ‘May thy fruits be sweet’? They are sweet already; that your shade be pleasant? It is already pleasant; that a stream of water may flow beneath you? Look, a stream of water flows already beneath you; therefore [I say], ‘May it be God's will that all your shoots shall be just like you.
Pirkei Avot 3:7
(7) Rabbi Elazar of Bartuta says: Give Him what is His, for you and yours are His. And so says David, "For all things come of Thee, and of Thine own have we given Thee" (I Chronicles 29:14). Rabbi Shimon says: He who is walking on his way while repeating his studies, and interrupts his studies and says, 'How lovely is this tree! And how lovely is this newly plowed field!' is deemed by Scripture to be as if he was guilty [of an offense punishable by the forfeiture] of his life.
Pirkei d’Rabbi Eliezer chapter 34:
Six voices go from one end of the world to the other and the sound is not audible… When a fruit-bearing tree is cut down the voice cries out from one end of the world to the other, and its sound is not audible… When the soul departs from the body the voice goes out from one end of the world to the other, and its sound is not audible….