contains no doubt once they realise that these men slept for more than three hundred years and then rose exactly as they had been, without the slightest change. The One who preserved them in that state is surely able to restore bodies even after worms have consumed them, and to revive the dead even after their flesh and bones have crumbled to dust—something the believers never question.
“His command, when He wills a thing, is only to say to it, ‘Be!’ and it is” (Yā Sīn 82).

The pronoun in the phrase “so that they might know” may refer to the Companions of the Cave themselves, for their own certainty is more forceful than anyone else’s; it may also include everyone. Allah knows best.

Next the Almighty said: “They will say, ‘Three, their dog the fourth’; and they will say, ‘Five, their dog the sixth’—guessing at the unseen; and they will say, ‘Seven, and their dog the eighth.’” Thus He set out the people’s disagreement about their number, citing three opinions, weakening the first two and confirming the third. This shows that the third is the truth: had the reality been otherwise He would have mentioned it, and had it been false He would have refuted it.

Since dispute over such matters brings no benefit, Allah taught His Prophet ﷺ the proper decorum when people differ in this way: say, “Allah knows best.” Hence His words: “Say: My Lord knows best their number.” And: “None knows them except a few”—that is, a few of humankind. “So do not argue about them except with an obvious, easy argument, and do not ask anyone about them.” For this reason Allah left their number unspecified at the beginning of the story—“They were young men who believed in their Lord”—for had there been great advantage in stating it, the Knower of the seen and the unseen would have done so.

The Almighty also said: “Never say of anything, ‘I shall certainly do that tomorrow,’ without adding, ‘If Allah wills.’ And remember your Lord when you forget, and say, ‘Perhaps my Lord will guide me to something nearer to right conduct than this.’” This is a noble etiquette to which Allah has directed His servants. Whenever someone says, “I will do such-and-such tomorrow,” he should add, “If Allah wills,” thereby affirming his resolve, for the servant does not know what tomorrow holds, nor whether what he intends is actually decreed. This “exception” is not merely formulaic; it is real. Ibn ʿAbbās said it remains effective for up to a year, though in certain situations the time-frame may vary. The same principle appears in the story of Solomon, peace be upon him, when he said: “Tonight I shall visit seventy women; each one will bear….”