Tafsir of Hud 11:68

(As if they had not dwelt therein) meaning, as if they had not resided in it—that is, in their homes. The sentence is said to be in the position of a circumstantial qualifier (hal), meaning they became (prostrate), resembling one who had never existed and had never occupied a place at all.

(Verily, Thamud)—the noun is used in place of the pronoun for the sake of explicit clarification. Hafs and Hamza deemed it diptote (prevented from declension with tanwin) by regarding it as a tribe. The majority of the seven reciters deemed it triptote (declined with tanwin), regarding it as a clan, as we mentioned previously. It is also said that it is regarded as the name of the great forefather; thus, the intended meaning is the first ancestor, and it is declinable. In that case, an omitted genitive addition is implied, such as "the offspring of" or "the children of," and so on. It is further said that it is declined with regard to the first perspective, while maintaining its form, even if the intended meaning here is the tribe.

(Disbelieved in their Lord)—He explicitly stated their disbelief, despite it being known from their previous conditions, in order to revile their state and to provide the rationale for their deserving the imprecation against them of ruin and destruction in His, the Glorified's, statement: (Verily, away with Thamud).

Al-Kisa'i alone read it with tanwin (in Thamuda). The discussion regarding the explanation of their story has already preceded in the most complete manner.