Tafsir of Qaf 50:23

(And his companion will say, "This...")

That is, the devil who was assigned to him in the worldly life, as Mujahid has said. In the Hadith, it is stated: "There is no one except that he has been assigned a companion from among the jinn." They asked, "Even you, O Messenger of Allah?" He replied, "Even me, except that Allah the Exalted has helped me against him, so he has submitted and does not command me except with good."

( "...is what is with me, ready.")

This is an allusion by the disbelieving person himself—that is, "This is what I have with me and in my possession, prepared for Hell, having readied him for it through my misguidance and leading him astray." This does not contradict what the Exalted has narrated about the companion in His upcoming saying: ("His companion will say, 'Our Lord, I did not make him transgress...'") because this is analogous to the statement of Satan: ( "And I will surely mislead them") and his saying: ( "And I promised you, but I betrayed you"), whereas that is analogous to his saying: ( "And I had no authority over you except that I invited you...").

Qatadah and Ibn Zayd said: His companion is the angel assigned to drive him, who says, pointing to him: "This is what is with me, present."

Al-Hasan said: It is the scribe of his evil deeds, who says, pointing to what is in his scroll: "This is what is written with me, ready, prepared for presentation."

It has also been said: His companion here is his own deeds, both of the heart and the limbs, though this holds no weight.

Ma (what) is an indefinite noun qualified by the adverbial phrase and by ‘atīd (ready), or it is a relative pronoun (mawṣūla) with the adverbial phrase serving as its conjunction. ‘Atīd is a predicate after a predicate for the demonstrative pronoun, or it is the predicate of a deleted subject. It has been permitted that it could be a substitute (badal) for ma, based on the principle that it is permissible to substitute an indefinite noun for a definite one—even if it is not described—if the benefit is achieved through that substitution.

As for estimating it as shay’in ‘atīd (a ready thing), based on the notion that the substitute is the deleted described noun whose adjective has taken its place, or that the relative ma, due to its ambiguity, resembles an indefinite noun, thus allowing a substitute to be taken from it—it has been argued against that this is weak. This is because the first implies the deletion of the substitute, which grammarians have rejected, and the second is not upheld by those who stipulate that it must be an adjective; thus, it is a settlement without the consent of the two litigants.

‘Abdullah recited it as ‘atīdan in the accusative case, functioning as a state (ḥāl).