The Torah portion of Vaes’chanan contains the commandments to recite Shema and study Torah.1 Although both commands are found in the same verse, they are very different.

The duty to recite the Shema involves reciting it twice daily, “when you lie down and when you rise.” Each recitation is an entity unto itself, the proof being that the blessing for its recitation is itself recited twice daily, in the morning and in the evening.

The obligation to study Torah, however, is not divided into the two separate times, but is a single, ongoing obligation that continues throughout the day and night. This is why the blessing for Torah study is recited only once a day.

Seemingly, the very opposite should be the case: Torah study is bound up with comprehension and comprehension varies according to time — when a person is rested he will think more clearly, etc. Since comprehension is affected by time, it would be logical to link the command of Torah study — an act that requires comprehension — to time, and to its division of day and night.

The mitzvah of reciting the Shema, however, requires a constant and unalterable acceptance of the yoke of the Heavenly Kingdom and G‑d’s Unity. Thus, it stands to reason that this command should not be subject to the changes that result from the division of night and day.

Nonetheless, we find that the commandment of Shema is linked to time, while the command to study Torah defies the divisions of time.

Why is this so?

Man’s life is subject to the division of days, for “Days separate one from the other”2 — days divide time into distinct entities. To have a complete “day,” night and day must be combined, as the verse states,3 “…there was evening and there was morning, one day.”

This also hints at the ultimate purpose of man’s service — to transform this nethermost world into a dwelling place for G‑d. The implication is that man should not negate physicality, but rather that this lowly world, seemingly separate from the spiritual realms, should become a dwelling place for G‑d.

This is accomplished when the physical organism itself comes to realize that its whole essence derives from G‑d. When this connection is felt by a corporeal being, G‑d’s absolute unity is revealed.

An allusion to this concept can be found in the Torah when it states: “…there was evening and there was morning , one day.” The implication is that the Divine intent is to combine and unite the darkness and corporeality of “evening” with the luminosity and ethereality of “morning,” so that together they form one day.

This idea of unity within diversity lies at the heart of the Shema , wherein the Jew declares: “Shemah Yisrael… the L-rd is One ,” thus “crowning G‑d and making Him reign ‘above, below and on all four sides’“4 by revealing His light and oneness within this physical and spiritually dark world.

Thus, connecting the mitzvah of Shema with the time periods of day and night emphasizes the unification of light and darkness, physical and spiritual, so that together they form “one day” — the revelation of G‑d’s unity within this world.

Torah, however, is likened to fire, as the verse states:5 “My words are like fire, says the L-rd.” Our Sages explain:6 “Just as fire is impervious to [ritual] impurity, so too is Torah impervious to [spiritual] impurity.” In other words, while Torah clothes itself in material reality and deals with physical matters, it remains detached from physicality.

Since Torah views the world from its own perspective rather than becoming one with creation, it follows that the obligation to study Torah is not subject to the limitations of night and day.

Based on Likkutei Sichos Vol. XIV, pp. 21-23.