Tafsir of As-Saffat 37:58

This is a return to conversing with his companions after completing the speech directed at his peer, out of boastfulness and joy for the great grace and everlasting bliss that Allah the Exalted has granted him, and to reproach his peer. It is also permissible that it is the speech of all those questioning, or a continuation of the speech of the speaker addressing his peer by way of rebuke. The first view is preferred.

The hamza is for confirmation (taqrir), and it contains the meaning of astonishment. The fa is for conjunction with a preceding phrase implied by the structure of the speech, as maintained by al-Zamakhshari and his followers—that is: "Are we to be immortal? Are we, then, not to die?" meaning, not from those whose state is death, as indicated by the sifat mushabbaha (active participle/adjective). It was also recited as (bima'itin).