Tafsir of Al-Baqarah 2:226

(For those who swear off their wives) Ila’, as Al-Raghib said, is an oath that implies deficiency in the matter concerning which one swears, from the words of the Almighty: (They will not fail to corrupt you), i.e., [they will not] neglect [to cause you] harm, and (Let not those among you who are blessed with grace and abundance swear). In Islamic law, it has become an expression for an oath that prevents intercourse with one's wife.

So (yuluna), i.e., they swear, and (min nisa’ihim), with the omission of the genitive, or the noun is made to stand in place of the intended verb for the sake of emphasis. The oath concerning intercourse is connected with min (from) because it contains the meaning of distancing; as if it were said: They distance themselves (from their wives) while swearing. It is said that this verb is transitive through both min and ‘ala. Abu al-Baqa’ reported from some linguists that it is transitive through min. It is said that [the min] therein means ‘ala (upon), and it is said it means fi (in), and it is said it is redundant. It is permitted to consider the prepositional phrase a stable predicate (zarf mustaqir), meaning: There is established for them (from their wives) (a waiting period of four months).

It was read (alu min nisa’ihim). In the Mushaf of Ubayy it is (for those who swear [yaqsimuna]), which is narrated from Ibn Abbas—may Allah be pleased with them both. Tarabbus is waiting and pausing, and it is attributed to the prepositional phrase by way of extension, treating the adverbial object like a direct object, while the meaning remains that of adverbiality. It is the subject, and what precedes it is the predicate, or it is the agent of the prepositional phrase according to the view of Al-Akhfash regarding the permissibility of its functioning even if it is not supported [by a preceding verb].

The sentence, on both estimations, is in the position of an exception from His words, the Almighty: (But He will hold you accountable for what your hearts have earned). This is because Ila’, since one of two matters is necessitated by it—expiation upon breach without sin, or divorce upon fulfillment—differs from all other oaths, where accountability is determined by both or one of them according to Al-Shafi’i, or by afterlife accountability according to Abu Hanifa—may Allah be pleased with him. It is as if it were said: Except for Ila’, for its ruling is other than what was mentioned, and that is why this sentence was not conjoined to what preceded it.

After the Almighty mentioned that those who swear off their wives have a waiting period of four months, He explained its ruling with His words, the Exalted in Majesty: (Then if they return), i.e., they go back within the period, (then indeed Allah is Forgiving, Merciful), due to the oath they committed out of oppression and the firm resolve of the heart upon that breach, or on account of the return and the expiation. This is supported by the recitation of Ibn Mas’ud: (Then if they return within them).