Tafsir of Al-Kahf 18:30

{Indeed, those who have believed} — The phrase is in the position of providing a justification to urge toward faith, which is understood from the [previously mentioned] option. It is as if it were said: "And for those who have believed." Perhaps the change in structure is to signal the complete incompatibility between the states of the two parties. That is: those who believed in the truth that is revealed to you {and did righteous deeds}—as has been clarified throughout its context—{Indeed, We do not allow to be lost the reward of him who has done righteous work.}

Isa al-Thaqafi recited "la nuda''i" (We do not cause to be lost) with the doubling of the consonant [taḍ'īf]. In both readings, the sentence is the predicate of the second "inna." The predicate of the first "inna" is the second "inna" along with what is contained within its scope, and the linking element [rābiṭ] is an implied pronoun; its estimation is "from among them" [minhum]—that is, "the reward of those who did righteous work among them."

It cannot be objected that this implies that some of them have done righteous work while others have not, because that is only if "min" is taken as partitive [tab'īḍiyyah], which is not definitively the case, as it is possible for it to be explanatory [bayāniyyah]. Even if it is granted [as partitive], there is no harm in it, for "righteousness" [iḥsān] is that you worship Allah as if you see Him. However, this would leave the status of those among them who did not achieve righteousness in this sense unresolved.

Alternatively, the linking element is the apparent noun which is the subject in meaning, according to the view of al-Akhfash, who considers it a linking element; for those who truly did righteous work are indeed those who believed and did righteous deeds. This was objected to on the grounds that the indefiniteness of "work" [‘amalan] rejects it, as it signifies minimization [taqlīl]. It was answered that it is not necessarily for that, as an indefinite noun can denote generality in affirmative statements, and the context of praise is a truthful witness to that. Or, the linking element is the generality of "whoever" [man], based on the view that generality can serve as a link, as in the statement "Zayd, what an excellent man he is," according to one opinion; though this contains an obvious point of contention.