Whenever the Quran was being revealed to the Prophet ﷺ, he would hasten to recite it in order to memorize it. So Allah revealed "Do not move your tongue with it" up to His words "its collection and its recitation are upon Us" [Qiyamah 75:16–17].
كان النبي ﷺ إذا نزل القرآن عليه يعجل بقراءته ليحفظه، فأنزل الله عز وجل {لا تحرك به لسانك} إلى قوله {وقره أنه}
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It was narrated by Nasai in Kubra (11572) and Ibn Jareer in his Tafsir (23/496-497), both through chains from Sufyan bin Uyayna, from Amr bin Dinar, from Saeed bin Jubayr, from Ibn Abbas, who said, and then he related it. Ibn Jareer added, Ibn Abbas said, "Like this," and he moved his lips.This verse indicates that the Prophet ﷺ had no need to repeat the verses of the Quran for memorization as is customary, but rather Allah Himself took charge of making him memorize it. This is one of the greatest miracles of the Prophet ﷺ. His saying, "Indeed, it is upon Us to collect it and recite it" [Qiyamah 75:17], means that Allah first gathered the Quran in the breast of the Prophet ﷺ, and then the companions collected it in written pages and hides by the Prophet's ﷺ command. In this way, the word of Allah was fulfilled, "Indeed, it is upon Us to collect it and recite it" [Qiyamah 75:17]. See the details of this at the beginning of the tafsir.His saying, "Then it is upon Us to make it clear" [Qiyamah 75:19], means that Allah is the One who took charge of explaining the meanings of the Quran, and He inspired this to the Prophet ﷺ. So the sunnah is one of the two types of revelation, except that it is not recited.