﴿ وَمِنَ ٱلَّيْلِ فَسَبِّحْهُ وَإِدْبَٰرَ ٱلنُّجُومِ ﴾

“and extol His glory at night, and at the time when the stars retreat.”

and glorify Him at night — also in actual utterance — and at the receding of the stars idbāra is a verbal noun that is to say also glorify Him after these have set; or it means in the case of the former perform the two evening prayers and in the case of the latter the two units rak‘a of the dawn prayer or — it is said — the morning prayer.