In the opening verse of the portion Tzav we read that “The burnt-offering shall remain on the firewood on the altar all night until morning.”1 Rashi comments:2 “This teaches us that the fat and the limbs may be burned the entire night.”

Although the priests were to endeavor to do the burning by day — this being the most appropriate time3 — they could also do it throughout the night, in order to obey the command “Do not allow the fat of My offering to remain… until morning.”4

The Ramban states5 that the offering of an animal upon the altar was able to achieve atonement for a sinner because the person realizes that everything transpiring with the animal should have been happening with him, were it not that G‑d in His kindness permitted the substitution.

It is thus understandable that all aspects of an offering, including the burning of fat and limbs, find corollaries in terms of man’s spiritual service.

How does “burning the fat” apply to our spiritual lives?

Fat is indicative of pleasure.6 The lesson here is: “All fat is to be offered to G‑d7 — all of a Jew’s pleasure and satisfaction should be offered to G‑d.

This is why the main purpose of burning the fat is achieved by day. “Day” and “night” symbolize man’s spiritual states: day is the condition in which one’s soul shines within its body; night refers to a person who lacks this spiritual illumination.

The “day person” feels G‑dliness not only while engaged in Torah study and mitzvah performance, but the whole day through — even while engaged in mundane affairs. For this individual is sensitive to the G‑dliness that permeates the world. He is thus able to serve G‑d even while engaged in mundane actions — “In all your ways you shall know Him.”8

The “night person” lacks this spiritual sensitivity and illumination. Thus, this person must struggle while engaged in mundane affairs to see that such actions are done “for the sake of heaven” and not for selfish pleasure. It goes without saying that unlike the “day person,” the “night person’s” mundane actions are not elevated to holiness.

Moreover, the “night person” must be on guard even while engaged in the study of Torah and the performance of mitzvos : Since Torah is clothed in human intellect and mitzvos are garbed in the physical world, a person who lacks spiritual illumination must toil mightily to be sure that his Torah study is done purely for the sake of Torah, and not for the intellectual pleasure it causes. And so too with his performance of mitzvos.

Thus, while each kind of individual sacrifices his pleasure to G‑d, “day people” do so in a positive manner — their entire delight in even mundane affairs is that of G‑dliness. “Night people,” however, cannot truly say that their entire pleasure is G‑dly. Their spiritual toil lies mostly in subduing their baser instincts, and in seeing to it that whatever they do should at least be “for the sake of heaven.” Thus, their primary manner of service is the negation and suppression of evil.

This is why “offering the fat to G‑d” — dedicating one’s pleasure to holiness — is achieved principally by those on the level of “day,” while the burning of fat by night reflects the forestalling of transgression through the negation and subdual of evil.

Although lacking the spiritual intensity of a soul unencumbered by the body, the service of the average soul — struggling to elevate the body and the world — contains elements superior to the soul’s service prior to its incarnation.

Based on Likkutei Sichos , Vol. III, pp. 948-952.