Tafsir of Al-Anbiya' 21:101

{The best}: The preferred quality in goodness, the feminine form of al-aḥsan (the best). It refers to either:

• Felicity.
• The glad tidings of reward.
• Or being granted success in obedience.

It is narrated that Ali (may Allah be pleased with him) recited this verse and said: "I am among them, as are Abu Bakr, Umar, Uthman, Talha, al-Zubayr, Sa'd, Sa'id, and Abd al-Rahman ibn Awf." Then the prayer was called, and he stood up dragging his cloak, saying:

{They will not hear its faint sound}: Al-ḥasīs is a sound that is perceived.

{And what their souls desire}: Al-shahwah is the soul’s seeking of pleasure.

It is also recited as: {It will not grieve them} (lā yuḥzinuhum), from the verb aḥzana (to cause grief).

{The greatest terror}: It is said to be the final blast of the Trumpet, based on the words of the Exalted: “On the day the Trumpet is blown, and all who are in the heavens and on the earth are terrified” (al-Naml: 87).

• Al-Hasan said: It is being turned toward the Fire.
• Al-Dahhak said: It is when the Fire is sealed shut.
• It is also said: It is when death is slaughtered in the form of a white-and-black ram.

{The angels will meet them}: They will welcome them at the gates of Paradise, saying: "This is the time of your reward which your Lord promised you; it has arrived."

{The Day We will fold the heaven like the folding of a scroll for the records. As We began the first creation, We will repeat it. [That is] a promise binding upon Us. Indeed, We will do it.}