Tafsir of Al-Kahf 18:4

And to warn those who say, "Allah has taken a son," is linked to a specific group among those included in the previous warning of the "severe punishment," in order to signal the absolute monstrosity of their state due to the extreme hideousness of their disbelief and misguidance, as indicated by what follows. That is to say: and to warn, from among these disbelievers, specifically those who utter such a grave offense—namely, the Arabs who say the angels are the daughters of Allah (Exalted is He), the Jews who say Uzair is the son of Allah (Glorified is He), and the Christians who say the Messiah is the son of Allah (Mighty and Majestic is He).

The omission of the description following the relative pronoun—as seen in His saying, "And to give good tidings to the believers," etc.—is to signal that what is contained within the relative clause is sufficient to signify the most repulsive form of disbelief. The preference for the past tense verb is to indicate that the utterance of this ugly statement has definitely been issued by them in the past.

Some have made the omitted object in the preceding verse refer to this specific group. In the verse, there is the device of ihtibak (mutual ellipsis), where what is mentioned later is omitted from the first part—which is the "warned party"—and what is mentioned first is omitted from the latter part—which is the "thing warned against." This was challenged on the grounds that it results in the exclusion of all other categories of disbelievers from the warning and the threat.

It was countered that the warning of the other categories and their inclusion in the threat is known a fortiori (by priority), because the claim of divine sonship, even if it is a grave word, is subordinate to the act of shirk (polytheism). However, this view is open to criticism. Ibn Atiyyah estimated the object to be "the worlds," and Abu al-Baqa' estimated it to be "the servants," which would thus include the believers as well. This was challenged on the grounds that such generalization necessitates interpreting the "warning" as merely informing of a harmful matter, without considering the actualization of the "thing warned against" upon the "warned party," as in His saying, "Warn the people and give good tidings to those who believe." This leads to the noble arrangement of the text being devoid of evidence regarding the actualization of the "severe punishment" upon those other than this specific group. So, reflect upon this.