During the day
According to the above—that the burning of the fats is expressive of sacrificing one’s pleasure to G-d—the reason that the burning of the fats should be done during the daytime, and that only if one has not done so, may he burn them at night, can be understood as it relates to man’s service of G-d.
Day is the time of light, and in a spiritual sense, is expressive of revelation. Daytime is associated with the study of Torah and doing Mitzvos, as King Shlomo writes:
For a mitzvah is a candle, and the Torah is light, and disciplining rebukes are the way of life.
Mishlei 6:23
Daytime represents the period that an individual is involved in learning Torah and doing mitzvos, while nighttime is expressive of when the person is involved in their own pursuits.
The burning of fats—the pleasure—should be fulfilled preferably during the daytime:
This teaches, that concerning one’s own pursuits (represented by the nighttime), it is obvious that he should not be involved in them for his own pleasure and that they should rather be done for the sake of Heaven.
However, concerning Torah and mitzvos, a person is likely to convince himself that since he is involved with holy things, his actions are inherently good, no matter how he goes about performing them, as long as he is involved with learning Torah and doing mitzvos.
His rationale will be predicated on the following statement of the Sages:
A man should always occupy himself with Torah and good deeds, though it is not for their own sake, for through [doing good] with an ulterior motive, there comes [doing good] for its own sake.
Talmud, Pesachim 50b
A person is likely to think, that because the Torah tells him to continue doing Torah and mitzvos though he has ulterior motives, he can be satisfied with remaining at such a level.
However, this mentality is not correct, and such is the lesson of burn the fats during the daytime.
It is specifically in one’s Torah learning and fulfillment of mitzvos that one must make sure he is doing them in the proper way, and sanctifying his pleasure to G-d.
This guarantees that he will indeed learn Torah properly. For, if he is learning Torah for his own pleasure, he will not be bothered if his ideas are not in line with the ultimate truth of Torah; he is satisfied that he is enjoying the intellectual study of its wisdom.
This though, is not the case with a person who sanctifies their personal pleasure of learning to the Almighty. If such a person would develop a novel insight in Torah, which is not in line with the commentators (and therefore, not expressive of the truth of Torah), he will “burn” his pleasure. His intent is to understand the truth of Torah and not merely to enjoy the intellectual stimulation.
