"And We made your sleep a rest," meaning: drowsiness. Muhammad said: The root of "sabt" is the cessation of movement; it is said: a "sabūt" man, and he has been "subita."
﴿وَجَعَلنَا نومكم سباتا﴾ يَعْنِي: نُعَاسًا.
قَالَ مُحَمَّدٌ: أصلُ السَّبتِ: انْقِطَاعُ الْحَرَكَةِ؛ يُقَالُ: رجلٌ سبُوتٌ وَقد سُبت.