It may also refer to the day on which Allah lets His vengeance descend upon them; they will try to escape, but it will be too late for flight.

“When they sensed Our might, they began to run from it. ‘Do not run away! Go back to the luxury you once enjoyed and to your dwellings, so that you may be questioned.’” (al-Anbiyāʾ 21:12–13)

Next He reminded them of Joseph’s prophethood in Egypt, of the kindness he had shown people in both their worldly and religious affairs, and of the fact that this Messenger—Moses—is from Joseph’s own line, calling humankind to profess Allah’s oneness, worship Him alone, and shun all partners besides Him.

He also made clear that the people of Egypt in that era were, by disposition, prone to denying the truth and opposing the messengers. Hence His words: “You never ceased to doubt what he brought you until, when he died, you said, ‘Allah will never send a messenger after him,’” meaning that you rejected all of this.

Therefore He said: “Thus does Allah lead astray every extravagant doubter—those who dispute Allah’s signs without any authority that has come to them.” That is, they rebut Allah’s proofs, evidences, and demonstrations of His oneness without possessing any warrant from Allah. Such conduct is utterly detested by Allah; He abhors anyone who engages in it. “Thus does Allah seal every arrogant, tyrannical heart.” The verse is recited both as a genitive construction and as an adjective; both convey the same meaning. Whenever hearts oppose the truth—and they only oppose it without proof—Allah stamps them, i.e., He seals them.

Allah, Exalted is He, also says: “Pharaoh said, ‘Haman, build for me a lofty tower so that I might reach the ways—the ways of the heavens—and look upon the God of Moses, though I indeed think he is a liar.’ Thus the evil of Pharaoh’s deed was made attractive to him, and he was barred from the path; Pharaoh’s scheming ended only in ruin.” (Ghāfir 40:36–37)

Pharaoh denounced Moses as a liar in his claim that Allah had sent him, and he foisted his own fabrication upon his people when he said: “I know of no god for you other than myself; so kindle for me, Haman, a fire upon clay and build me a tower, that I may look upon the God of Moses—for I think he is among the liars.” In the present verse he says: “Perhaps I may reach the ways—the ways of the heavens—and look upon the God of Moses; yet I indeed think he is a liar.”

This utterance admits two possible meanings: (1) Pharaoh deemed Moses a liar for asserting that the universe has a Lord other than Pharaoh; or (2) he deemed him a liar in claiming that Allah had sent him. The first fits Pharaoh’s outward stance, for he denied the very existence of a Creator, whereas the second is closer to the wording here, for he says, “so that I may look upon the God of Moses,” that is, I will ask Him whether He has really sent Moses, “and I indeed think he is a liar” in that claim.

Pharaoh’s only aim was to prevent the people from believing Moses and to urge them to reject him. Allah, Exalted is He, therefore says: “Thus the evil of Pharaoh’s deed was made alluring to him, and he was diverted from the path.”