Tafsir of Al-Waqi'ah 56:46

"And they used to persist" (i.e., they were extreme, refrained from desisting, and were constant) "in the great sin" (meaning the grave transgression).

Some have interpreted al-hinth as a grave sin, rather than sin in the absolute sense. This is supported by the fact that it originally signifies a grave deviation; therefore, describing it as "great" is an intensification of its description—much like how a tawd, which is a massive mountain, is also described as "great." This is the intended meaning, as reported from Qatadah, al-Dahhak, and Ibn Zayd, and it is the apparent interpretation.

'Abd bin Humayd narrated from al-Sha'bi that what is meant by it is the major sins; it is as if he rendered the meaning: "And they used to persist in a great sin." In another narration from him, it is the yamin al-ghamus (the false oath), and its apparent usage is absolute.

Taj al-Din al-Subki said in his Tabaqat: "I asked the Sheikh—meaning his father, Taqi al-Din—what is 'the great sin' (al-hinth al-'azim)? He replied: 'It is the oath denying that which is alluded to by the words of the Almighty: And they swore by Allah their strongest oaths that Allah will not resurrect those who die.'"

This is a sound interpretation, because even if al-hinth is interpreted as sin in general or as a grave sin, its common usage is in the breach of an oath. This has been critiqued by the observation that the words of the Almighty refute it: [continuing to the next verse].