The Medrash (Rabba Vayikra 25:2, 3) on the passuk that commands the Jews to keep the Mitzva of Orla (not eating from the fruits of a tree, during its first three years of growth) says the following. R' Yehuda ben Pazi said, "Adam (Harishon)! You were commanded not to eat from the tree and could not hold out for too long. Now, your children wait three years before they eat the fruits from a tree."
The Medrash continues. R' Yehuda bar Simon expounds on the passuk from this week's parsha. In the way of Hashem you should go. How can one 'go in the way' of Hashem? Hashem is compared to a consuming fire? R' Yehuda bar Simon answers that the passuk means that one should try to emulate Hashem. Just as the first thing Hashem did in this world was planting trees, so too, when the Jewish people enter Eretz Yisrael they should involve themselves with planting trees and keeping the Mitzva of Orla.
The connection between planting trees and keeping the Mitzva of Orla with emulating the ways of Hashem needs explanation. As well, although both are tree related, what is the deeper connection between eating from Eitz Hada'as and the Mitzva of Orla? Regarding the Mitzva of Orla, the Zohar explains (3:87a), that the reason for this Mitzva is to nullify (through three years of growth) the strength of the earth (physical) from the food we eat.
This as well, was intended by the commandment not to eat from the Eitz Hada'as. It was a commandment that was to last only for three hours. (See Sanhedrin 38b, Sha'ar Hakavanos Drushei Rosh Hashana 1). Had Adam Harishon not eaten from the tree until the arrival of Shabbos, it would have raised the level of all food to an exalted level, including the fruits from the Eitz Hada'as. Instead of raising the earth to the level it was supposed to reach, the opposite happened; now man would have to return to earth.
The Medrash Tanchuma (Kedoshim 14) gives another lesson learned from the Mitzva of Orla; how to raise a child. The first three years of his life he cannot understand the smallest idea of service of Hashem. From three and on he learns to recite pessukim (תןרה צוה לנו משה וגו') and so on. Another lesson from trees is the fact that the labor going into planting and cultivating trees does not produce immediate results. One has to wait a while to enjoy the fruits of his labor. The same is true regarding our work in this world. The reward for our withstanding tests is not seen immediately. It is saved for later. This is why the first test of all mankind was with a tree. To impart this lesson to the world.
The fact that many lessons in service of Hashem are learned from trees is also why we find that the righteous are compared to trees in various ways (see Kiddushin 40b, Avos 3:20).
Based on this, we can now understand the Medrash that says that we must go in the ways of Hashem by emulating Him and the Medrash gives the example of planting trees and observing the Mitzva of Orla. This will also explain how the Mitzva of Orla rectifies the original sin.
