Ibn Isḥāq said:
It has reached me that the Messenger of Allah, peace and blessings be upon him, began the surah by reciting:
“All praise belongs to Allah, who has sent down the Book to His servant” (Q 18:1).
That is, [Allah is addressing] Muhammad: “You are My Messenger, proving the truth of what they asked about concerning prophethood.”
He continued: “and has allowed therein no deviation—[it is] upright” (Q 18:1), meaning that He revealed it in perfect balance, free of any inconsistency.
Ibn Isḥāq then mentioned the commentary on the surah up to Allah’s words:
“Or do you think that the Companions of the Cave and the Inscription were among Our wondrous signs?” (Q 18:9).
[The meaning is:] they did not appreciate the measure of My power, nor all that I have wrought in creation, nor the proofs I have established against My servants—proofs far greater than that.
Mujāhid said, “The affair of the Companions of the Cave is not the most astonishing of Our signs; there is a sign even more astonishing than it.”