a son who would fight in the cause of Allah.
They said to him, “Say: If Allah wills,” but he did not say it. He then went round to them, yet none of them conceived except a single woman, who delivered a half-formed child.

The Messenger of Allah ﷺ said,
“By Him in whose hand is my soul, had he said, ‘If Allah wills,’ he would not have broken his oath and would have obtained what he desired.”

As for His words, “And remember your Lord when you forget” (al-Kahf 24), forgetfulness may come from Satan; the remembrance of Allah drives him from the heart, and one recalls what he had forgotten.

And His words, “And say, ‘Perhaps my Lord will guide me to something nearer to right conduct than this’” (al-Kahf 24) mean: whenever a matter becomes confused, its circumstances unclear, and people’s opinions about it contradictory, turn to Allah, and He will make it easy for you and smooth the way.

Then He said: “And they remained in their cave three hundred years, and they added nine” (al-Kahf 25). Because the length of their stay carries great benefit, Allah mentioned it. The additional nine are lunar years, completing three hundred solar years, for every hundred lunar years is three years shorter than a hundred solar.

“Say: ‘Allah knows best how long they stayed’” (al-Kahf 26)—that is, when you are asked about such matters and have no transmitted report, refer the affair to Allah. “To Him belongs the unseen of the heavens and the earth”—He alone knows the unseen and discloses it only to whomever He wills among His creation. “How perfectly He sees and hears!”—He places everything in its proper place because of His complete knowledge of His creatures and of what they deserve.

He then said, “They have no protector apart from Him, and He allows no one to share in His rule” (al-Kahf 26): your Lord alone possesses sovereignty and disposes of affairs single-handedly; He has no partner.