Surah 15. Al-Hijr, Ayah 9

I.e., the Qur'an. The grammatical form nazzalna implies a gradual revelation ("step by step") over a period of time, as has been pointed out by Zamakhshari in his commentary on 2:23 (see the last sentence of my corresponding note [14]).

This prophecy has been strikingly confirmed by the fact that the text of the Qur'an has remained free from all alterations, additions or deletions ever since it was enunciated by the Prophet in the seventh century of the Christian era; and there is no other instance of any book, of whatever description, which has been similarly preserved over such a length of time. The early-noted variants in the reading of certain words of the Qur'an, occasionally referred to by the classical commentators, represent no more than differences in respect of diacritical marks or of vocalisation, and, as a rule, do not affect the meaning of the passage in question. (See also note [11] on 85:22 , explaining the expression lawh mahfuz.)

The purity of the text of the Qur-an through fourteen centuries is a foretaste of the eternal care with which Allah's Truth is guarded through all ages. All corruptions, inventions, and accretions pass away, but Allah's pure and holy Truth will never suffer eclipse even though the whole world mocked at it and were bent on destroying it.