Tafsir of Al-Anbiya' 21:34

(And We did not grant to any human being)—whoever they may be—(before you immortality), meaning eternal life and remaining in this world, for it contradicts both creational and legislative wisdom. It has been said that al-khuld means a long duration, from which comes their referring to the cooking stones as khawalid (enduring). This has been used as evidence against the life of al-Khidr, peace be upon him, though there is debate regarding this.

(So if you die)—according to the dictates of Our wisdom—(would they be the eternal ones?)

This was revealed when they said, "Wait for him the uncertainty of fate." The first fa (so) is to connect the conditional sentence to what preceded it, and the hamza is for the denial of its content; in reality, it is for the denial of its consequent, meaning what comes after the second fa. Yunus claimed that this clause is the focus of the denial, while the condition is a parenthetical insertion between them, and its response is omitted, indicated by that clause and not by itself. This includes the denial of what was mentioned—the denial of that upon which their existence or non-existence revolves, specifically their gloating over the death of the Prophet (peace and blessings be upon him). It is as if it were said: "If you die, will they be the ones to live forever, such that they should gloat over your death?"

In the same vein is the saying of Imam al-Shafi’i (may mercy be upon him): Men wished that I would die; and if I die, that is a path on which I am not the only one. So say to him who desires otherwise than what has passed: "Provide for another life like this one, as if it were already here."

And the saying of Dhu al-Isba’ al-Adwani: When time drags its burdens upon a people, it settles them upon others. So say to those who gloat over us: "Wake up! The gloaters will encounter just as we have encountered."

The scholar al-Tibi mentioned—and the author of al-Kashf transmitted it with a slight addition—that this is a return to that for which the noble Surah was composed regarding Prophethood, in order to transition from it to the establishment of another legislation. This is because Allah the Exalted has silenced those who claimed He had taken a son and those who attributed partners to Him, and rebuked them by mentioning what indicates their silencing, which is His saying, "So if you...", because when the opponent has no remaining foothold, he wishes for the destruction of his adversary.