Tafsir of Al-Mu'minoon 23:112

(He said) — meaning Allah, exalted be His majesty, or the angel commanded to do so, not some of the leaders of the people of the Fire as has been suggested— in order to remind them of how long they remained in the world to which they requested to return, after alerting them to the impossibility of such a return. In this, there is a rebuke for their denial of the Hereafter.

Hamza, al-Kisa'i, and Ibn Kathir read (Say) as an imperative addressed to the angel, not to some of the leaders as has been claimed, nor to all of the disbelievers by way of substituting the singular for the plural as al-Tha'alibi asserted.

(How long did you remain on earth) — which you claim you wish to return to— meaning, how long did you reside therein while alive?

(Number of years)

(Number) is a specifier (tamyiz) for "how long" (kam), and it is an adverb of time for the verb "remained" (labithtum). Abu al-Baqa' said: "(Number) is a substitute (badal) for 'how long' (kam)."

Al-A'mash and al-Mufaddal, on the authority of 'Asim, read "number" ('adadan) with tanwin. Abu al-Fadl al-Razi said: "Years" (sinin) is accusative as an adverb, and "number" ('adadan) is an infinitive (masdar) substituted in place of the noun; it is an adjective placed before the noun it describes. The suggestion that the meaning of "remained" (labithtum) is "counted" ('adadtum) is far-fetched. Abu al-Baqa' said: "Years" (sinin) in this reading is a substitute (badal) for "number" ('adadan).