▪ Jeffery1938: »The early authorities differed widely as to what the Siǧǧīn of this eschatological passage might be. It was generally agreed that it was a place, but some said it meant ‘the lowest earth,’
al-ʔarḍ al-sābiʕaẗ, or a name for hell, or a rock under which the records of men’s deeds are kept, or a prison.
1
The Qurʔān itself seems to indicate that it means a document,
kitāb marqūm, so al-Suyūṭī,
Mutaw, 46,
2
tells us that some thought it was a Pers word meaning ‘clay’ (tablet). Grimme,
ZA, xxvi, 163, thinks that it refers to the material on which the records are written, and compares with the Eth [Gz]
ṣəngʷən or
ṣəngūn meaning ‘clay writing tablets’. It is very probable, however, as Nöldeke,
Sketches, 38, suggested long ago, that the word is simply an invention of Muḥammad himself. If this is so, then
kitāb marqūm is probably an explanatory gloss that has crept into the text.«