Tafsir of Al-Muzzammil 73:12

"Indeed, with Us are shackles" (ankāl), which is the plural of nikl, with the nūn vowelled with either a kasra or a fatḥa. It is a heavy shackle. It is also said that it refers to iron chains. The first definition is more recognized in the language. It is narrated from al-Sha'bi that the shackles were not placed on their feet out of fear that they would escape, but rather, whenever they attempt to rise, the shackles pull them down.

The sentence serves as a justification for His saying—Exalted is He—"Leave Me and those who [deny the truth]," and whatever is conjoined to it. It is as if it were said: Entrust their entire affair to Me and grant them respite, for I possess that with which I shall take the severest vengeance upon them—shackles and a jaḥīm (a fire of intense burning).