Tafsir of Al-Mutaffifeen 83:29

"Indeed, those who committed crimes..." [is a narration regarding some of the abominations of the polytheists of Quraysh—Abu Jahl, al-Walid ibn al-Mughirah, al-As ibn Wa'il, and their cohorts]. This was brought forth as a prelude to mentioning some of the states of the righteous in Paradise.

"They used to"—that is, in the worldly life, as Qatadah stated—"laugh at those who believed." They would mock their poor, such as Ammar, Suhayb, Khabbab, Bilal, and others among the destitute. In al-Bahr, it is narrated that Ali (may Allah honor his countenance) and a group of believers with him passed by a gathering of the disbelievers of Mecca, who laughed at them and treated them with contempt. Thus, "Indeed, those who committed crimes..." was revealed before Ali (may Allah honor his countenance) reached the Messenger of Allah (may Allah bless him and grant him peace).

In al-Kashshaf, this is narrated regarding the hypocrites, claiming they said, "Our Lord is the bald one today," meaning their leader, Ali (may Allah honor his countenance). They only said this in mockery. Perhaps the first [account] is more correct.

The placement of the prepositional phrase [at the beginning] is either for the purpose of restriction (qasr), signifying the extreme heinousness of what they did—meaning they used to laugh at those who believed, despite the obvious fact that they were not entitled to do so—following the methodology of the Almighty's saying, "Is there doubt about Allah?"—out of consideration for the verse endings (fawasill).