Yirmiya Perek 17
In פרק יז, פסוקים ה - ח the נביא compares two different people to trees: "אָרור הַגֶבֶר אַשֶר יִבְטַח בָאָדָם...וְהָיָה כעַרעָר בָעַרָבָה וְלא יִרְאֶה כִי יָבוא טוב" - “Cursed is the man who has faith in Man...he is like a lone tree in the desert and does not see when good comes.”
Conversely, ירמיה describes:
"בָרוך הַגֶבֶר אַשֶר יִבְטַח בַה...וְהָיָה כְעֵץ שָתול עַל מַיִם...וְהָיָה עָלֵהו רַעַנַָן...וְלא יָמִיש מֵעַשות פֶרִי” - "Blessed is the man who believes in Hashem...he is like a tree planted by water...whose leaves are constantly fresh...and which does not stop producing fruit."
Why does ירמיה compare people to trees? Let us look at a mishnah in Pirkei Avos at the end of Perek Gimmel:
'Rabbi Yaakov said: One who walking along and interrupts his learning and remarks: “מה נאה אילן זה! ומה נאה ניר זה!” "How beautiful is this tree! How beautiful is this ploughed piece of land!" he is considered as baring guilt for his soul' - i.e. he deserves to die!
First, this seems a little harsh; is one not meant to appreciate nature? Secondly, the mishnah's examples of beautiful things - a tree and a ploughed piece of land - seem interesting.
A fascinating answer has been put forward, which provides a deeper understanding of trees.
What is unique about a tree and ploughed piece of land? Both represent enormous potential; the ploughed land is ready to provide food or wine and a tree can provide wood, fruit or shade. But Torah has higher spiritual propensity than all physical potential, and so if one interrupts Torah learning for physical potential, he is “Held guilty for his soul”. He has selected physicality over his soul’s eternally greater potential.
Furthermore, the passuk compares the one who has a lack of faith in Hashem, he who puts physical potential over spirituality, as one who does not see when טוב, good, comes. The Torah is in fact called טוב (as in כי לקח טוב נתתי לכם תורתי אל תעזובו), and this is analogous to what the physical potential should be used for, namely to enable spiritual closeness to Hashem. Often we get carried away with the physical world and do not see “כי יבוא טוב” - that the Torah is there waiting for us to grab it. However, someone who believes in Hashem will be able to have a meaningful connection with Him and the Torah.