when the address in it is to a group (1), while His statement: "a disbeliever" is singular? And do we permit—if that were permissible—for someone to say: "Do not be the first man who stood up"?

It is said to him: The singular form is only permissible for that to which afʿal is annexed when it is the predicate for a group (2) if it is a noun derived from a verb, because it conveys the omitted intended element alongside it in the sentence, which is "who" (man), and stands in its place in conveying the meaning of plural and feminine that man would convey, while being singular in its wording. Do you not see that you say: "Do not be the first of those who disbelieve in it"? For man carries the meaning of a group (3), and it is indeclinable in the manner of nouns for dual, plural, and feminine. Thus, when the noun derived from a verb is put in its place, it functions while singular in the same way man functions in expressing plural and feminine meanings, just as in your saying: "The army is retreating" and "the troop is approaching" (4), where you make the verb singular due to the singular wording of "army" and "troop". But it is impermissible to say: "The army is a man" or "the troop is a boy" unless you say: "The troop are boys" and "the army are men", because a singular noun from among nouns that are not derived from a verb does not convey the collective sense of a group. Of this is the statement of the poet:

And when they eat, [he is] the vilest eater... and when they go hungry, [they are] the worst of the hungry (5)

So he used the singular once, in accordance with what I described regarding the implicit sense of man and substituting the explicit noun derived from a verb in its place, and he used the plural another time by matching the number of the nouns