Tafsir of Al-Jathiyah 45:11

(This) refers to the Quran, as indicated by what follows and what precedes it, such as "hears the verses of Allah," "and when he learns of our verses," and "these are the verses of Allah which We recite to you." (Guidance) in the ultimate state of perfection, as if it were guidance itself. (And those who disbelieved in the verses of their Lord) meaning the Quran as well, given that the genitive construction refers to the covenantal reference. Although the apparent construction would have been to use a pronoun, it was avoided in favor of the manifest arrangement of the majestic text to further denounce their disbelief in it and to expose the hideousness of their state. It is also permissible that the "verses" intended here include the Quran and others.

(And for them is a punishment of Rijn) from the most severe of punishments, (painful).

(Painful) in the nominative case is an adjective for "punishment," following the rhyme.

Several among the seven reciters read "Al-alim" (painful) in the genitive case, as an adjective for "Rijn," while also considering it an adjective for "punishment." The view that the genitive is due to proximity (adjacent grammar) is something that should not be given credence. It has been said—regarding the reading in the nominative—that "Rijn" carries the meaning of "Rijs" (filth), which is impurity. The meaning would be: for them is a painful punishment consisting of swallowing filth or drinking filth, and what is intended by this is the pus that the disbeliever swallows and can hardly gulp down. However, there is no call for this interpretation, as is not hidden. The tanwin (nunation) on "punishment" in all three occurrences signifies magnification, and its nominative case is either due to it being an initial subject (mubtada) or due to the prepositional phrase serving as the acting agent (fa'il).