Sun and moon, each in an orbit

Ibn Kathir on "toward its stopping point". He gives two views. The first, place: it "refers to its fixed course of location, which is beneath the Throne". The second, time: "this refers to when the sun's appointed time comes to an end, which will be on the Day of Resurrection", with Qatada: "It has an appointed time and it will not go beyond that." He also reports that Ibn Masʿud and Ibn ʿAbbas recited the verse as "with no fixed course" (lā mustaqarra lahā), which he explains as "never slowing down or stopping". The same page also has his description of the Throne: "a dome supported by legs or pillars, carried by the angels, and it is above the universe", and "the Throne is the roof of creation and it is not a sphere as many astronomers claim" (surahquran.com, 36:38). That is the cosmology of his time.

Al-Jalālayn. "to its resting-place in other words it does not overstep it", and "its running is the ordaining of the Mighty in His kingdom the Knower of His creation".

Maʿārif al-Qurʾān. The word "is used to denote place of rest as well as time of rest"; on the time view, the sun reaches "the end of its movement already determined - and that time is the Day of Doom"; on the place view, it is "a place where one orbit of the movement of the sun stands completed".

On the moon and the orbits. Ibn Kathir: the moon wanes "until it appears like the old dried curved date stalk", which Ibn ʿAbbas explains as the stem joining the date cluster to the tree. "Each in an orbit" means "floating, i.e., revolving, in their orbits in the heaven". He cites Ibn ʿAbbas "and others among the Salaf" (the earliest generations): "In an orbit like the arc of a spinning wheel", and lists Ibn ʿAbbas, ʿIkrima, al-Dahhak, al-Hasan, Qatada and ʿAtaʾ al-Khurasani for the "floating, revolving" reading. On "nor does the night overtake the day", Mujahid says: "They seek one another rapidly"; Ibn Kathir explains that "there is no gap between night and day; each of them follows the other with no interval".

The hadith of the sun's prostration. Abu Dharr (ra) reports that at sunset the Prophet (pbuh) asked him, "O Abu Dharr! Do you know where the sun sets?" and said: "It goes and prostrates underneath (Allah's) Throne", then recited 36:38 (Bukhārī 4802 Ṣaḥīḥ (sound)). In the fuller report, it "takes the permission to rise again", and a time will come when "it will be ordered to return whence it has come and so it will rise in the west" (Bukhārī 3199 Ṣaḥīḥ (sound)). Both are in Sahih al-Bukhari.

How scholars read the prostration. They differ, and the differences are worth stating:

• Al-Khattabi, Aʿlām al-Ḥadīth (commentary on al-Bukhari): "It cannot be denied that it halts beneath the Throne, in a manner that we cannot see or comprehend" (IslamQA's translation). For him the manner belongs to the unseen.
• Ibn Hajar, Fatḥ al-Bārī, offers several readings without insisting on one: it may be "the prostration of the angel charged with it", or the sun "prostrates by the state it is in", that is, by its submission. He reports Ibn al-ʿArabi: "Some people denied its prostration, though it is sound and possible", while others read it as the sun's permanent state of subjection (SeekersGuidance's renderings).
• Maʿārif al-Qurʾān calls the prostration "simply a similitude in consonance with the mores of effective prophetic teaching": the sun "is nowhere but under the ʿArsh, at all times and at every place", so it "at every moment while moving on its orbit keeps offering sajdah" and "needs no pause or break".
• Ibn Kathir (in al-Bidāya wa al-Nihāya, cited by SeekersGuidance through al-Qastallani) holds that "nothing in this hadith says the sun ascends above the heavens to prostrate": it sets from our sight while continuing in its orbit.

What the commentators did not say. None of the commentaries read here describes the sun moving through a galaxy. Their cosmology was that of their time; Ibn Kathir reads the orbits as "in the heaven".