Sayyiduna Ibn Abbas (may Allah be pleased with them both) narrated that when the Qur'an was revealed to the Messenger of Allah (peace and blessings be upon him), he (peace and blessings be upon him) would try to receive it hastily with his tongue and lips, and he (peace and blessings be upon him) had to endure great hardship in this. So Allah, the Mighty and Majestic, revealed this verse: "Do not move your tongue with it to hasten it" [Surah al-Qiyamah: 16], meaning: do not try to grasp it hastily. "Indeed, upon Us is its collection and its recitation" [Surah al-Qiyamah: 17], meaning: We will gather it in your chest and make you recite it. "So when We have recited it" [Surah al-Qiyamah: 18], meaning: when We have revealed it, "then follow its recitation" [Surah al-Qiyamah: 18], meaning: listen and remain silent. "Then upon Us is its explanation" [Surah al-Qiyamah: 19], meaning: We will make it clear through your tongue. After that, the Messenger of Allah (peace and blessings be upon him) was at ease.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 12245