Tafsir of Al Imran 3:24

(That): meaning the aforementioned turning away and aversion, is a subject (mubtada') whose predicate is His saying:

(Because they said, "The Fire will not touch us except for a number of days"): That is, this [punishment] is accrued to them because of this statement, the belief in which has become firmly rooted in them, whereby they belittled tribulations and did not care, as a result, to commit sins and transgressions. The "number of days" refers to the days they worshipped the calf. It is mentioned here in the plural form (معدودات), unlike in [Surah] Al-Baqarah, where it is in the singular form (معدودة), as a stylistic variation in expression. This is because a broken plural for non-rational beings may sometimes be treated as a singular feminine, and other times as a plural of the feminine gender. One says: "These are stable mountains (jibalun rasiyah)," and if you wish, you may say "stable (rasiyat)," and "walking camels (jamalun mashiyah)," and if you wish, "walking (mashiyat)." The plural form was specifically chosen here due to its implication of scarcity, just like the noun it describes, which is more fitting for the context of expressing astonishment and denunciation.

(And they were deluded in their religion): meaning they were made to covet what is not to be coveted, and were deceived.

(By what they used to fabricate): Meaning their fabrication and lying, or that which they used to fabricate, such as their saying: "The Fire will not touch us," etc. This was stated by Mujahid. Or [it refers to] their saying: "We are the sons of God and His beloveds," as stated by Qatadah. Or it includes that and similar things, such as their saying: "Our forefathers are the prophets, and they will intercede for us," and "God Almighty promised Jacob that He would not punish his children except to the extent of fulfilling an oath."

The adverbial phrase is linked to what is before it, or to "they fabricate." This was challenged by Al-Khatib, who argued that what follows a relative pronoun (mawsul) cannot govern what precedes it. The response was given that this is permissible due to [linguistic] latitude.