Tafsir of Fatir 35:42

{And they swore by Allah their strongest oaths}—meaning they swore and exerted themselves in swearing to the utmost of their capacity—{that if a warner came to them, they would be more guided than any of the [previous] nations.} The pronouns refer to the Quraysh. The occasion for this was that before the mission of the Prophet ﷺ, it reached them that a group from the People of the Scripture had denied their messengers. They said: "May Allah curse the Jews and the Christians! Messengers came to them, and they denied them. By Allah, if a messenger comes to us, we will surely be more guided than any of the nations." When what happened occurred, Allah the Exalted revealed this verse.

{And if a warner came to them}: The verb is in the past tense to reflect the meaning; otherwise, they said, "if a warner comes to us." Likewise, {they would surely be} corresponds to this. {One of the nations}: "One" (ihda) here signifies a single nation. The apparent meaning is that it is general, even if it is indefinite in an affirmative context, because the context demands generality. The definition of "nations" (al-umam) is by reference (li-l-'ahd), and the intent is the nations that denied their messengers; meaning: "If a warner comes to us, we will be more guided than each of the nations—the Jews, the Christians, and others—so we will all believe, and none of us will deny." Or the intent is: "We will be more guided than a nation that is referred to as 'one of the nations'," as a means of preferring them over other nations. This is like saying, "He is the one of the people" or "the one of his era," and as they say, "He is one of the ones" (ahad al-ahadin) or "She is one of the ones" (ihda al-ahad), intending preference in intelligence and prowess. A poet said: "Until they consulted me, the one of the ones, a lion, a fierce beast, possessing complete weaponry."

Ibn Malik stipulated in al-Tashil that one may say of that which is deemed great and has no equal, "He is one of the ones." However, al-Damamini said in his commentary: "Its usage is only established in ihda and its likes when annexed to a plural derived from its own root, like ihda al-ahad and ahad al-ahadin, or annexed to a description, like 'one of the scholars' or 'one of the great ones.' As for annexation to generic nouns like 'nations,' it requires transmission [of authority]." I have scrutinized this, and it is established that ihda is used for magnification without any annexation at all; for they say of a great calamity, "It is one of the seven," meaning one of the nights of 'Ad in severity. Furthermore, expressions like "the one of his people," "the most singular of them," and "the most singular of his mother" have become common. No clear distinction appears between that which is annexed to a plural derived from the root, that which is annexed to a description, and that which is annexed to generic nouns. I do not think such a case requires [further] transmission; let this be reflected upon.

The author of al-Kashf said: "The indication of 'one of the nations' towards preference is not clear, unlike 'the one of the people' and its like." He then interpreted it as being in the style of [the verse]: "Or some souls meet their doom," meaning that the vague "some" might be intended to denote glorification, just like the indefinite [is used for that purpose], and ihda is like it. The response to this is that once its usage for magnification is established, its indication of preference is in the utmost clarity.

{But when a warner came to them}—and what a warner! He is the most noble of messengers, Muhammad ﷺ, as reported from Ibn Abbas and Qatada, and this is the most apparent interpretation. According to Muqatil, it refers to the splitting of the moon, but this is more obscure than the star Suha, and the context rejects it—{it did not increase them}—meaning the warner or his arrival—{except in aversion}, meaning turning away from the truth and fleeing from it. Attributing the increase to the warner is metaphorical, for he is the cause of it, and the sentence is the answer to "when" (lamma).

The verse has been used as evidence for the "litigious" (harfiyah) nature [of the conditional particle] due to the presence of negation, which prevents what follows from operating upon it, though there is a debate regarding this.