إِذْ يُغَشِّيكُمُ ٱلنُّعَاسَ أَمَنَةً مِّنْهُ وَيُنَزِّلُ عَلَيْكُم مِّنَ ٱلسَّمَآءِ مَآءً لِّيُطَهِّرَكُم بِهِۦ وَيُذْهِبَ عَنكُمْ رِجْزَ ٱلشَّيْطَـٰنِ وَلِيَرْبِطَ عَلَىٰ قُلُوبِكُمْ وَيُثَبِّتَ بِهِ ٱلْأَقْدَامَ
Iz yughashsheekumun nu'assa amanatam minhu wa yunazzilu 'alaikum minas samaaa'i maaa'al liyutah hirakum bihee wa yuzhiba 'ankum rijzash Shaitaani wa liyarbita 'ala quloobikum wa yusabbita bihil aqdaam
Remember when God wrapped you in sleep as reassurance from him, and sent down water from the sky to purify you with it, to remove from you Satan's defilement, to bind your hearts together, and to steady your feet.
Nuʿās names a shallow doze rather than deep sleep, the same word used of the believers after Uhud in 3:154. Here it falls the night before Badr, on men camped on soft sand while the enemy held the wells. Commentators differ over what the rain washed off, whether ritual impurity or the fear of men cut off from water, and the firmed footing underneath is left doing both jobs at once.