The mitzva to study Torah is a mitzva to know God’s ways. A person engaged in Torah study is engaged in the most elevated manifestation of faith. God will permantly rest His Presence on such a person.

It is a mitzva to study Torah every day, for Torah is the essence of the highest form of faith, which is to know the ways of the Holy One, blessed be He. For anyone who invests himself in Torah study is deemed meritorious in this world and in the World to Come, and he is saved from all the accusing angels. For the Torah is the secret of faith, as one who is engaged in it is engaged in the highest form of faith, and God rests His Presence within him such that it will never depart from him. (Zohar 2:134b)

God gave us the Torah so that through its study we can unite our souls with His holiness. If one studies Torah only for some tangible benefit rather than in order to cling to God and bring His light into the world, then the land will remain bereft of sanctity. This is a cause of destruction, as the Sages taught that the Land of Israel was destroyed “because they did not recite the blessing over the Torah” (Bava Metzia 85b), meaning that the Jewish people did not have the proper intention when studying Torah.

Further reading: For more on the Torah and its sanctity, see A Concise Guide to the Sages, p. 449.

We study Torah in order to cling to God:

God’s intent was always that we should engage in Torah study so that our souls would be empowered by the essence, spirituality, and sanctity of the Torah’s source. Therefore, the Holy One, blessed be He, gave the Torah of truth to Israel as a gift that will never be forgotten, so that all 248 limbs and 365 sinews of our souls and bodies should cleave to the Torah’s 248 positive mitzvot and the 365 negative mitzvot. If the Jewish people were to study Torah with this intent, they would become a chariot and sanctuary for His Presence. The Divine Presence would literally rest within them, as they are a sanctuary of God, and the Divine Presence would establish a permanent dwelling within them. The land would shine with His glory. This would connect the heavenly entourage with the entourage of the lower spheres, and the sanctuary would be unified.

Studying Torah for ulterior motives leads to destruction:

But then they transgressed this instruction and they engaged in Torah study only [to fulfill] their physical needs, for their benefit, in order to know the laws for the sake of business and to be haughty and to display their wisdom. They did not intend to be empowered and to cling to the sanctity and spirituality of the Torah and to draw the Divine Presence down to this earth so that their souls could be elevated to a great level after their deaths. Through this they caused a separation, for the Divine Presence was removed from the world and went up on high, and the land was left in its physicality, without sanctity. This caused its destruction and loss. (Rabbi Yoel Sirkis, Bayit Ĥadash, Tur, Oraĥ Ĥayyim 47)

God is completely beyond human comprehension, but He inserted His light into the Torah. When a person studies Torah and internalizes its knowledge, he contains within him the divine light and thereby achieves an unparalleled unity with God.

God can be grasped only through Torah and mitzvot:

God is referred to as the Infinite One, [as it is written,] “His greatness is unfathomable” (Psalms 145:3), and “The mind cannot grasp Him at all” (Tikkunei Zohar, Introduction 17a). The same is true regarding His will and His wisdom, as it is written, “There is no scrutinizing His understanding” (Isaiah 40:28), and it is written, “Would you discover the mystery of God” (Job 11:7), and it is written, “My thoughts are not your thoughts” (Isaiah 55:8). Regarding this, the [Sages] taught, “Wherever you find God’s greatness, you find His humility” (Yalkut Shimoni, Ekev 856). [This means that] God constricted His will and wisdom within the 613 mitzvot of the Torah and in their laws, as well as in the letter sequences of the Tanakh, with their homiletic explanations in the Sages’ commentaries. This enables any aspect of the soul residing in a human body to comprehend them with its mind and fulfill them with action, speech and thought, to the greatest extent possible.

When a person understands a halakha he unites with God and His wisdom:

When a person comprehends a certain ruling with his intellect, as a halakha set forth by the Mishna, Talmud or halakhic authorities, he thereby comprehends, grasps, and encompasses God’s will and wisdom with his intellect. The mind cannot grasp God Himself, or His will and wisdom, unless they are concretized in the halakhot outlined before us. Moreover, his intellect also becomes encompassed by them. This constitutes a wondrous unification, which is totally unparalleled in the physical world, actually achieving complete union and unification.

The advantage of learning and knowing Torah over fulfilling other mitzvot:

The mitzva of studying and comprehending the Torah has an infinitely great and wondrous advantage over all the [other] mitzvot [performed by bodily] action, including even the mitzva of speaking [words of] Torah. For in all mitzvot of speech and action, God enclothes and envelops the soul from head to foot in divine light. [However,] through the study of Torah, not only is the intellect enveloped in [the light of] divine wisdom, but the divine wisdom is also [contained] within him – what the intellect is able to comprehend, grasp, and encompass in the knowledge of Torah, according to each person’s intellect, and his ability to know and comprehend the literal, allusive, homiletic, and esoteric [meanings of the Torah]. (Rabbi Shneur Zalman of Liadi, Tanya, Likutei Amarim, chap. 4–5)

All of existence is dependent on our Torah study. If there were no Torah study in the entire world for even one moment, the entire universe would cease to exist. When we study Torah, God’s light is abundant in the world; when we decrease our study, God’s light in the world also decreases.

The life force and continued existence of all of the worlds is dependent upon our speaking and thinking about Torah. It is undoubtedly true that if the entire world, from one end to the other, were devoid of our engagement and contemplation in Torah even for a moment, God forbid, then all of the upper and lower worlds would be instantly destroyed and would turn into nothingness, God forbid. Similarly, the abundance of their [divine] light is dependent only on the extent of our engagement in Torah study. (Rabbi Ĥayyim of Volozhin, Nefesh HaĤayyim 4:11)

Torah study is beneficial to a person in many ways. However, a person’s motivation for studying Torah should be his love for Torah and for God. The Sages said: “Envy, lust, and honor drive a man from the world” (Avot 4:21). If one studies Torah because he is jealous of others or in order to receive benefits or honor from others, that study will drive him from the world.

One should study Torah only due to his love for it and not for any other reason. If he intends to study for any one of these three reasons [envy, lust, or honor], they will drive him from the world. Sometimes a person studies out of jealousy of another, as “jealousy among scribes increases wisdom” (Bava Batra 22a), and not out of love for the Torah itself…. Sometimes a person studies to fulfill his desires, for he knows that most people tithe their money and donate it to a Torah scholar, and therefore their desire brings them [to study]… The [mishna also] mentions “honor,” referring to one who studies for the honor he will receive, [such as that people allow him to be] the first to enter and the first to depart. Concerning [one who studies for any of] these three motivations, [the mishna] states that they “drive a man from the world,” for this is not Jacob’s portion; rather, one must study out of love for God, may He be blessed. (Rabbi Shmuel de Uçeda, Midrash Shmuel, Avot 4:21)

Further reading: For more on studying Torah properly, see A Concise Guide to the Sages, p. 454.