Torah Or and Likkutei Torah Maamarim of the Alter Rebbe (Shneur Zalman of Liadi)

The Torah is G-d's knowledge, which means that it is infinite. Therefore, there are different levels of the Torah, one deeper than the other. The hidden mystical aspect of the Torah is called Kabalah. Kabalah is often compared to wine; just as wine is hidden in the grape, and by squeezing the grape, wine is obtained, a similar analogy can be made with the Torah and Kabalah. The deepest and highest level of the Torah is Chassidut, which is compared to oil. Oil floats on top of all liquids indicating its superior quality. At the same time oil makes everything oily. Another characteristic of oil is that all substances contain oil. If any substance is pressed enough oil will be obtained; therefore oil is contained in the essence of everything. Chassidut is also the essence of the Torah, and within it is contained all the other levels. In Chassidut, not only are the mystical and Kabalistic dimensions discussed, but all the other levels are an integral part. Chassidut unifies all the different levels of the Torah for the purpose of elevating the world and the person himself, to make the world and the person G-dly. As a result the world becomes a dwelling place for G-d and causes the coming of Moshiach, the ultimate purpose of creation.