In the Garden of Eden there were two trees: the tree of life and the tree of knowledge. Adam ate from the tree of knowledge, and God expelled him from the garden so that he would not also eat from the tree of life. The Zohar explains that the Torah is the tree of life, and one who connects to Torah is connected to life. Involvement in worldly endeavors is considered involvement with the tree of knowledge, which ends in death. It is primarily through the deeper layers of the Torah and hasidic thought that the Torah serves as the tree of life.

The Torah through which the divine light is experienced is the tree of life:

The Written Torah is called the tree of life because it was not so enclothed in material expression, and the divine light is felt in it…. How much more so with regard to the mystical side of Torah, which was not enclothed at all in physical clothing, for it speaks of spiritual matters, the process of divine emanation, and divine matters in general. Comprehension of this [side of Torah] is spiritual cognition, and the divine light is felt in it. Its focus is to know God and to thereby come to love and revere Him…. This is especially true of the teachings of the Ba’al Shem Tov, of blessed memory, which our fathers, our holy rabbis, of blessed memory, may their souls rest in peace, have passed on to us. They reveal and explain the greatness and exaltedness of God, and all divine matters that lead to love and reverence of God. They teach us to know God and how to serve Him with love and reverence as is required of us, as well as the paths leading to it…. Therefore, the mystical side of Torah is considered the tree of life, for it reveals the divine and allows one to develop a complete heart, meaning love and fear of Heaven, which is the primary goal of all involvement in Torah and mitzvot.

It is a mitzva to study the mystical side of Torah:

Therefore, it is a mitzva and obligation for each and every person to study the mystical side of Torah…. One who does not study the inner Torah is responsible for the loss of his own life, for one can fall even through the study of Torah…. This is certainly the case for one who does not want to engage in this type of study and to study only the revealed aspect of Torah. He will cling to the “place of death”… and only with and through [the mystical side of Torah] will he merit the light of life, for it is the tree of life and through it he will come to love and fear of God. (Rabbi Shalom Dovber Schneersohn, Kuntres Etz HaĤayyim, chap. 11)

The Arizal (Rabbi Yitzĥak Luria) revealed many aspects of the inner Torah, and the Ba’al Shem Tov explained them and revealed how they are relevant for every individual’s service of God. Since every Jew has a divine soul, he can illuminate the darkness in his heart with divine light.

The main way that the Ba’al Shem Tov’s Torah sheds light is relevant only to the greatest sages in the world, for his teachings are a commentary on the mystical teachings that were earlier revealed by the Ari. The Ari spoke of matters dealing with the upper worlds and the holy spheres, whereas the Ba’al Shem Tov added and explained that all of this is relevant to the service of God of a Jew in this lowly world…. But since the Torah of the Ba’al Shem Tov is a holistic system, just as it is above all the worlds it is also below all the worlds. [It belongs to] every Jew simply because he is a Jew, since he has [within him] a portion of the divine. It can lift him from his lowliness and light up the darkness of his heart with the light of God, may He be blessed. The Torah of the Ba’al Shem Tov teaches us the way to raise up the light of the soul, hewn from the throne of glory, even in the simplest of Jews. (Rabbi Shalom Noaĥ Berezovsky, Netivot Shalom, Part 1, Ĥasidut 1)