وَٱلَّيْلِ إِذَا سَجَىٰ
Sentence structure
وَٱلَّيْلِ is coordinated as a genitive oath phrase. إِذَا سَجَىٰ is a time clause; سَجَىٰ has understood subject هُوَ.
Ayah summary
And by the night as it covers everything.
وَٱلَّيْلِ — And the night
Grammar: وَ coordinates; the defined masculine oath noun is genitive. An omitted circumstantial element is associated with «ٱلَّيْلِ».
إِذَا — when
Grammar: A temporal adverb introducing the following clause. This phrase is linked through an omitted element.
سَجَىٰ — it becomes still
Grammar: A third-person masculine-singular perfect with understood subject هُوَ.