Tafsir of Al-A'raf 7:90

(And the eminent among his people who disbelieved said) is a conjunction to the previous (The eminent said...). It is possible that these "eminent" are the same arrogant ones as before, with the change in the relative clause indicating that the basis for their previous statement was their arrogance, and this is a narrative of them leading others astray after narrating their own straying, according to one view. It is also possible that they are others, lower in rank, whose role was to mediate between the leaders and the common people, managing affairs according to the will of the arrogant.

Meaning, they said to the people of their nation—in order to repel them and deter them from faith, after they had witnessed the steadfastness of Shu'ayb (peace be upon him) and those who were with him among the believers in their faith, and they feared that the people would depart from them—"If you follow Shu'ayb and enter his religion and abandon the religion of your forefathers, you will then surely be losers."

That is, you will be cheated, because you exchanged guidance for error and because of the loss of what you gain through fraud and cheating in weight and measure. Thus, "loss" in the first interpretation is a metaphor, and in the second, it is literal. Ibn Abbas inclined toward the interpretation of "losers" as "the cheated," while it is reported from 'Ata' that it means "the ignorant," and from al-Dahhak that it means "the wicked."

"Idhan" (then) is a particle of response and recompense, interposed—as more than one scholar has stated—between the noun of "Inna" and its predicate. It is said: It is "Idha" (when), the adverbial particle of futurity, where the sentence to which it is added is omitted and replaced by the tanwin (nunation); however, Abu Hayyan refuted this, stating that no grammarian has ever said this.

The sentence is a response to the oath that is prefaced by the "lam" (in "la-khasirun"), evidenced by the lack of the letter "fa" connecting it. It occupies the place of the response to the conditional clause, and it is not a response to both simultaneously, as the words of some might suggest. This is because, as has been said, in addition to violating grammatical rules, it would require a single sentence to have a place in inflection while simultaneously having no place in inflection, even if that were permissible from two different perspectives.