Tafsir of An-Nazi'at 79:29

"And He darkened its night": That is, He made it dark. It is said, "The night became dark (ghatasha)," and "Allah the Exalted darkened it (aghtashahu)," just as it is said, "It became dark (zalama)" and "He darkened it (azlamahu)." It is also said, "The night became dark (aghtasha al-layl)," just as one says, "It became dark (azlama)." The terms "a dark night (laylah ghatsha)" and "a dark night (layl aghṭash)" have been used. Al-A‘sha said: "I slaughtered my camel for them at the waning of the night / And their night was pitch-black, dark (ghatash)." In Al-Bahr, citing Kitab al-Lughat fi al-Qur’an, it is stated that aghtasha means "it became dark" in the dialect of Anmar and Ash‘ar.

"And brought out its daylight": That is, He caused its daylight to appear. Al-Duha (the daylight/forenoon), in its origin—as understood from the words of al-Raghib—is the spreading of the sun and the extension of the day, then it was named for the well-known time, and became common in that usage. It is used metaphorically for the day as a whole by virtue of the contrast. It has been said that the speech contains an elliptical genitive (mudaf), meaning "the light of its sun," which acts as a metonym for the day. The first interpretation is closer. The day is expressed by al-Duha because it is the most noble and pleasant of its times, containing a revival of the spirits not found in others; thus, it is more fitting for the context of reminding those who deny the Resurrection and the return of souls to their bodies. It is also said that, for this reason, it is more deserving of mention in the context of bestowing favors.

The attribution of the night and the daylight to the heaven (al-sama’) is because they occur due to the setting and rising of the sun, which are celestial phenomena. Or, they occur due to its movement—according to the theory that the sun shares the motion of the celestial sphere—or they occur due to the sun’s movement within its orbit within the heaven—according to the view that the heaven and the celestial sphere are distinct, and that what moves is the star within the sphere, as is implied by the apparent meaning of His saying: "Each in an orbit is swimming," and that the sphere is merely the path of the star in the heaven.

It is also said they are attributed to it because they are the first to appear from it, as the beginning of the night is the approach of darkness from the direction of the east, and the beginning of the day is the rise of dawn and the approach of light from it. In al-Kashshaf, the night and the sun are attributed to the heaven because the night is its shadow and the sun is the lamp lit in its expanse. This was objected to on the grounds that the night is the shadow of the earth. The reply was given that this is a consideration of the viewer’s perspective, just as the ornamentation of the lowest heaven is also a consideration of the viewer’s perspective. It is also said that their attribution to it is based on the fact that they occur beneath it, and in this consideration, they encompass what barely crossed the minds of the Arabs: the night and day that each last for six months—the night and day at the ninety-degree latitude, where the rotation is circular. This was challenged on the grounds that they stated the conical shadow of the earth ends at the sphere of Venus, which is in the third heaven, thus the limitation is not exhaustive. There is scrutiny in this, so ponder it. In summary, the attribution is based on the slightest of connections.