COMMENTARY on 68:42
Mustafa Khattab:

Translation:
˹Beware of˺ the Day the Shin ˹of Allah˺ will be bared,5 and the wicked will be asked to prostrate, but they will not be able to do so,
Commentary:
5   Like the Face and the Hands, the Shin is believed by many to be one of the qualities of Allah, in a way befitting His Majesty and Greatness. Since baring the shin in the Arab culture is associated with the heat of battle, some interpret the verse metaphorically, so the meaning would be: “˹Beware of˺ the Day when horror sets in.”

 

A. Yusuf Ali:

Translation:
The Day that the shank 5622 shall be laid bare, and they shall be summoned to prostrate in adoration, but they shall not be able,-
Commentary:

5622  The Day that the Shin shall be laid bare, that is, when men are confronted with the stark reality of the Day of Judgement. On that occasion men will be summoned to adoration, not necessarily in words, but by the logic of facts, when the Reality will be fully manifest: the Glory will be too dazzling for the Unbelievers, whose past deliberate refusal, when they had freedom to choose, and yet rejected, will stand in their way. (R).

 

Muhammad Asad:

Translation:
on the Day when man's very being shall be bared to the bone, 21 and when they [who now deny the truth] shall be called upon to prostrate themselves [before God], 22 and shall be unable to do so:
Commentary:
21  Lit., "when the shin[-bone] shall be bared": i.e., when man's innermost thoughts, feelings and motivations will be laid bare. The implication is that their erstwhile claim that whatever is "expedient" is morally justifiable (see note 19 above), shall be revealed in all its nakedness - namely, as something indefensible and spiritually destructive.
22  I.e., willingly, gladly humbling themselves before Him.