"And by the night when it covers (saja)," means when it darkens.
Muhammad said: It is also said that saja means: it becomes still; and that is when its darkness reaches its peak and it settles.
Yahya said: This is an oath.
﴿وَاللَّيْل إِذا سجى﴾ إِذَا أَظْلَمَ.
قَالَ مُحَمَّدٌ: وَقِيلَ: سَجَى: سَكَنَ؛ وَذَلِكَ عِنْدَ تَنَاهِي ظَلامِهُ وَرُكُودِهُ.
قَالَ يَحْيَى: وَهَذَا قسم.
