Tafsir of Al-Waqi'ah 56:39-40

(A multitude from the former [generations]) (And a multitude from the latter [generations])

This is the predicate of an omitted subject—meaning: "they are a multitude"—or it is a second predicate for the subject implied alongside "in [orchards of] lote-trees," or it refers to "the People of the Right" in His saying: And the People of the Right—what of the People of the Right? Or, it is a subject whose predicate is omitted—meaning: "among them [are] a multitude"—or it is a subject whose predicate is the prepositional phrase preceding it. There are several possibilities.

The last of these [possibilities] has been objected to on the grounds that the meaning resulting from it is not apparent, nor does it possess eloquence. As for making the lam (in "li-ashab al-yamin") signify "from" (min), as it is used in the verse [referring to the poetry]: "And we are for you (or 'from you') on the Day of Resurrection the best," its condition is not hidden [i.e., it is weak].

The "former" and the "latter" are either from the [totality of] nations, or from this nation alone, according to what you have heard previously.

Furthermore, the Glorified did not say regarding the People of the Right, "as a reward for what they used to do," as He, the Almighty, said regarding the Forerunners; this is to symbolize that the grace bestowed upon them is purely [from His bounty], as if their deeds, due to their deficiency compared to the deeds of the Forerunners, were not counted as being of the same consideration.

Then, it is apparent that what has been mentioned regarding the state of the People of the Right is the ultimate state to which they arrive. Thus, it does not contradict the possibility that there may be among them one who is punished for sins he committed and died without having repented from them, and then enters Paradise. It is impossible to say that the sinful believer is of the People of the Left, because the explicit descriptions of them [the People of the Left] that follow necessitate that they were disbelievers. If one were to make this [the sinful believer] a separate category, it would imply that the classification is not exhaustive; so reflect upon this. And Allah, the Exalted, knows best.