Tafsir of Ash-Shu`ara' 26:192

This returns to what was mentioned at the beginning of the noble surah regarding the exaltation of the status of the Great Qur’an, and a refutation of what the polytheists said about it. Thus, the pronoun refers to the Qur’an.

It is also said: It is an affirmation of the truthfulness of those stories and an alert to the inimitability of the Qur’an and the prophethood of Muhammad (may Allah bless him and grant him peace); for the narration of such accounts by one who did not learn them cannot be anything but a revelation from Allah, the Almighty and Majestic. In this view, the pronoun refers to the aforementioned noble verses that speak of those recounted stories.

It is also permitted that it refers to the Qur’an, of which these stories are a part. The expression of this being a "revelation" (tanzil) is for the purpose of hyperbole. The intent is that it is truly sent down from Allah, the Exalted. His description, may He be glorified, as the Lord of the worlds is to signal that its revelation is from the manifestations of His nurturing, the Almighty and Majestic, and His compassion for all.