Tafsir of Al-Kahf 18:103

(Say) O Muhammad, (shall we inform you) an address to the disbelievers. If the interrogative is interpreted as seeking permission, it contains mockery. The plural form in the first person is used, as it is said, to designate him from the beginning of the matter, and to notify the believers that this news is known to them as well.

(Of the greatest losers in works) It is in the accusative case as a specifier (tamyīz). It is pluralized, even though the origin of the specifier is the singular, and the verbal noun (maṣdar) encompasses both the few and the many, as mentioned by the grammarians. This is only when the verbal noun remains in its state of being a verbal noun; however, if it is interpreted as an active participle, it is treated accordingly. Here, aʿmāl (works) functions as ʿāmilīn (those performing/workers), so it is pluralized to aʿmāl. The attribute can occur as a specifier, such as: "To God is his praise as a horseman." Some claimed that aʿmāl is the plural of ʿāmil (worker), but this was challenged, noting that the pluralization of the fāʿil pattern to afʿāl is rare, and some grammarians denied it except for specific terms, such as ishhād as the plural of shāhid. It was also said: it is the plural of ʿamal like katif, meaning "possessor of work," as stated in the Qāmūs, but this is as you see.

Some later scholars claimed that if aʿmāl is considered to mean ʿāmilīn, then al-akhsarīn must mean al-khāsirīn (the losers), because when the specifier is an attribute, it is an expression of the one from whom it is derived, united with it in essence and predicated upon it through compatibility. Grammarians have even stated that it is made into a state (ḥāl) as well, and it is a predicate of the subject of the state in meaning. It is evident that the superlative (afʿal of superiority) cannot be identical to the active participle due to the aspect of excess; thus, wherever the active participle occurs as a specifier and is in the accusative case due to the superlative, it must mean the active participle so that they may be unified. Some challenged this by saying that the superlative with the definite article al- cannot be stripped of the meaning of superiority, just as it cannot be stripped of it when followed by a genitive construction; that only happens when it is followed by min (than), as Ibn Malik explicitly stated in al-Tashīl, and as Al-Radi mentioned. It is not hidden from you what is in all of this of scrutiny. The truth is that the pluralization is for nothing other than what was mentioned first. Yes, Abu al-Baqa’ mentioned that it is pluralized because it is in the accusative case as active participles, and he interpreted this by saying that he intended the linguistic meaning by the active participle, and intended it to be pluralized to signify distribution, although this is not free from some objection.

Furthermore, this—according to what is in Irshād al-ʿAql al-Salīm—is an exposition of the condition of the disbelievers regarding the deeds they performed that were good in themselves and in their estimation, as they were impressed by them, confident in attaining their reward, and expecting to see their effects, following the exposition of their conditions regarding their deeds that were evil in themselves while being good in their estimation.