Tafsir of Ar-Rum 30:32

{From among those who split their religion}: This is a substitute (badal) for "the polytheists" (al-mushrikin), with the preposition repeated. Their splitting of their religion refers to their differences regarding what they worship, according to their diverse whims. It is also said: it refers to their differences in their beliefs despite having a unified object of worship. The benefit of this substitution is a warning against affiliating with any of the sects of the polytheists, by clarifying that all of them are in manifest error.

Hamza and al-Kisa'i read it as {faraqu}, meaning: they abandoned their religion which they were commanded to follow, or that which their natural disposition (fitra) necessitated.

{And became sects}: i.e., divisions, where each faction follows its leader who paved the way for its religion, established it, and set its foundations.

{Each faction, with what they have}—of crooked religion founded upon deviant opinion and false claims—{are rejoicing}: i.e., happy, thinking that it is the truth.

It is said that the sentence is a parenthetical confirmation of the content preceding it regarding their splitting of their religion and their status as sects. It is also said that it is in the place of an accusative because it acts as an adjective for {sects}, with an implied pronoun [referring back to it], meaning: "each faction among them." Some have claimed it is a state (hal). It has also been permitted that {rejoicing} be an adjective for "each" (kull), as in the verse of al-Shamakh: "And every friend, if he does not humble himself to connect with a friend, becomes cutting or hostile." In this case, the predicate (khabar) is the preceding prepositional phrase, namely His saying: {From among those who split their religion}. Thus, it would be disconnected from what precedes it. This has been criticized on the basis that in such constructions, the genitive modifier (mudaf ilayh) is what is described, as Shaykh Ibn al-Hajib explicitly stated regarding the saying: "And every brother, his brother is separated from him / By your father’s life, except for the two stars (al-Farqadan)." However, in al-Bahr, it is stated that describing the genitive modifier in such constructions is the most common usage, and he cited the verse: "Every eye poured upon it tears, and they left every garden like a dirham." As for what was said—that if "each" (kull) is described by it, it indicates that the rejoicing encompasses everyone and is therefore more eloquent—this is invalid. On the contrary, the opposite is more eloquent, if one were to contemplate it even slightly.