Tafsir of Al-Hijr 15:63

(They said: "Nay, we have come to you with that about which they were in doubt.")

Meaning: With the torment that you used to threaten them with, while they were doubting, questioning, and denying it. They have thus laid bare the matter and clarified the plain truth to him—peace be upon him—so how could any distress or impatience afflict him after that? This was stated by the scholar Abu al-Sa‘ud, and it is a rational interpretation. He treated "Nay" (bal) as an interjection (idrab) canceling out what he—peace be upon him—had supposed regarding the abandonment of his support. The meaning is: "We have not abandoned you, nor have we left you alone to face them; rather, we have come to you with that which will destroy them—the torment that they used to deny when you threatened them with it."

More than one scholar, after interpreting his—peace be upon him—statement "with that which you have heard," has treated it as an interjection canceling the cause for the aforementioned fear, in the sense of: "We have not come to you with that for which you disapprove of us, but rather we have come with that in which lies your joy, your happiness, and your vindication against your enemy," which is the torment he used to threaten them with while they denied him. They did not say "with their torment," despite the purpose being achieved, so that the speech might contain consolation from two aspects: the realization of their torment and the realization of his—peace be upon him—truthfulness. In this is a reminder of the denial he used to endure from them.

It is said: He—peace be upon him—alluded to his fear and his apprehension [by saying] that they were strangers (deniers), so they countered him—peace be upon him—with a better and more beautiful allusion. I see no obstacle to interpreting the speech as an allusion according to what we have reported from the scholar as well. Perhaps the placing of this dialogue before the argument that took place between him and the people of the city—as he said—was for the sake of hastening to mention the good tidings to Lot—peace be upon him—regarding the destruction of his criminal people and the salvation of his family, following the mention of the good tidings given to Abraham—peace be upon him—regarding both. Since that required explaining the manner of salvation and the arrangement of its precursors, it was indicated summarily; then the action of the people and what was done to them was mentioned. There was no concern for changing the chronological order, trusting in its observance in another place.

The attribution of the coming with the torment to him—peace be upon him—despite it being sent down upon the people, is by way of entrusting its command to him, as if they brought it to him and entrusted its affair to him so that he might dispatch it upon them just as he used to threaten them with it. Thus, the letter 'ba' (in 'bi-ma') is for causation (transitive), and it is also permissible that it be for accompaniment (being associated with).