فَغَشِيَهُمْ مِنَ الْيَمِّ مَا غَشِيَهُمْ
Then there overwhelmed them from the sea what overwhelmed them. (Ṭā Hā 20:78)
The phrase “مَا غَشِيَهُمْ” leaves the precise magnitude of the overwhelming sea unenumerated. This compact reference creates a sense of enormity rather than reducing the event to a catalog of particulars.
Here the relative expression serves magnification (tafkḥīm / tafkhīm). It does not follow that every relative phrase is deliberately vague: the previous example used its clause for precise identification, whereas this one gains force through purposeful non-specification.