{And those who avoid the major sins and immoralities, and when they are angry, they forgive}

(And those who avoid...)—in conjunction with what follows—is either a coordination to the first relative pronoun [in verse 36], or it is a praise in the nominative case, serving as the predicate of an omitted subject, or in the accusative case as an object of an implied verb such as "I mean" or "I praise." The waw (and) is parenthetical, as Al-Radi stated. Abu al-Baqa’ overlooked the waw, failing to mention the coordination and suggesting substitution instead.

"Major sins" (kaba'ir al-ithm) refers to whatever has been met with a threat of punishment, or whatever necessitates a legal penalty, or everything that Allah the Exalted has forbidden. "Immoralities" (al-fawahish) are those sins whose indecency and ugliness are extreme. It has been said: "Major sins" refers to matters concerning heresies and the fabrication of doubts; "immoralities" refers to matters concerning the appetitive faculty; and His saying, "And when they are angry, they forgive," refers to matters concerning the irascible faculty. This [interpretation] is as you see it.

"Sin" (al-ithm) here refers to the genus; otherwise, it would have been phrased as "sins" (al-athame). "When" (idha) is a temporal adverb for "they forgive." "They" (hum) is a subject, not an emphasis for the pronoun within "they are angry"—though Al-Bahr permits this. The sentence "they forgive" is its predicate, and its fronting [before the verb] is to denote exclusivity, as they are the conceptual agents. Their exclusivity lies in the fact that they are uniquely worthy of this [quality] compared to others, for forgiveness during the state of anger is a rare example. The verse hints that they forgive even before [the offender] seeks forgiveness.

It is said that "they" is in the nominative case due to a verb that "they forgive" explains; when it was omitted, the pronoun became detached [as a separate pronoun], but this is weak. Abu al-Baqa’ treated "when" (idha) as a conditional particle and the sentence "they forgive" as its response, but Abu Hayyan critiqued this by noting that it would then require a fa (the connective particle), and its omission is not permitted except in poetry. You have already encountered that which is useful as a reminder, so keep it in mind.

Hamzah and Al-Kisa'i recited it as "major sin" (kabir al-ithm) in the singular, intending the genus or the perfect example of it, which is polytheism (shirk). It is narrated from Ibn Abbas—may Allah be pleased with them both—that it is interpreted as such. This does not necessitate redundancy, because the intent is continuity and constancy.