«وَتَحْسَبُهُمْ أَيْقَاظًا وَهُمْ رُقُودٌ»
“You would think them awake, while they were asleep.”
A-yqāẓan (“awake”) and ruqūd (“asleep”) are two nominal expressions referring to opposite states. Their juxtaposition sharpens the distinction between appearance and reality.
This is ṭibāq between nouns. The grammatical category and the passage’s meaning should both be identified.