Tafsir of An-Naml 27:86

"Have they not seen that We have made the night to rest therein"—The vision here is of the heart, not of the eyes, because although the essence of night and day are visible things, the making of them as described is among the conceptual matters. It means: Do they not know that We have made the night, with its darkness, so that they may find tranquility within it through stability and sleep? One of the rajaz poets said: "Sleep is the rest of the sensory powers from movements and of the psychological powers."

"And the day as a source of sight"—meaning, so that they may perceive, through the light within it, the paths of undertaking their livelihood. It is an act of hyperbole that "seeing" (which is the state of the people) is made into the state of the day and one of the descriptions it was created with, such that it cannot be separated from it. This approach was not taken for the night because the influence of the night's darkness on "resting" is not on par with the influence of the day's light on "seeing." It is well known that the verse contains the rhetorical device of ihtibak (mutual ellipsis), with the implied meaning being: "We have made the night dark so they may rest in it, and the day as a source of sight so they may disperse in it."

"Indeed, in that"—the use of the demonstrative pronoun here, which carries a sense of distance, serves to indicate the high degree of its merit—"are signs"—great signs—"for a people who have certainty."

It points to Oneness (Tawhid), the possibility of the Resurrection, and the sending of the Messengers (peace be upon them). This is because the succession of light and darkness in a specific manner—not fixed by the nature of the matter itself—cannot occur except by a compelling Power, which is not possessed by what the polytheists associated with Him. Furthermore, He who is capable of replacing darkness with light in the same substance is capable of replacing death with life in the substances of the bodies. And He who made the night and the day as causes for their benefits and interests is surely not one to neglect that which is the pivot of all their interests in their livelihood and their afterlife: the sending of the Messengers (peace be upon them).

In Irshad al-'Aql al-Salim, it is stated: "Signs, many and great, for a people who believe, indicating the validity of the Resurrection and the truthfulness of the verses that speak of it—a clear indication. How could it be otherwise when one who reflects upon the succession of the night and the day, and their alternation in wondrous ways founded upon exquisite wisdoms—which baffle the intellects in their comprehension and which none can encompass except the knowledge of Allah, the Glorious and Exalted—and witnesses in the horizons the transformation of the darkness of the night (mimicking death) into the brightness of the day (resembling life), and observes in himself the transformation of sleep (the brother of death) into wakefulness (similar to life), shall conclude with firm conviction that the Hour is coming, no doubt about it, and that Allah Almighty will resurrect those in the graves. He shall judge that Allah has made this a model and a proof to be used as evidence for its realization, and that the verses speaking of it—and the state of the night and day—are a proof for it, and that all other verses are Truth sent down from Allah Almighty."

Perhaps the first interpretation is more appropriate, especially when the similarity between sleep/wakefulness and death/life is added to the reasoning for the possibility of the Resurrection, as this contains a hidden subtlety of evidence. The believers are specifically mentioned because they are the ones who benefit from the signs. The connection of this verse to the preceding one is that it acts as proof for the validity of the Resurrection contained therein.