Saeed bin Jubayr reported,

Ibn Abbas said regarding the words "Do not move your tongue with it to hasten it" [Qiyamah 75:16] that whenever Jibreel came down to the Messenger of Allah ﷺ with revelation, he would move his tongue and lips along with it, and this was difficult for him, and it could be seen on him. So Allah revealed the verse in Surah "I swear by the Day of Resurrection", "Do not move your tongue with it to hasten it. Indeed, upon Us is its collection" [Qiyamah 75:16–17], meaning it is upon Us to gather it in your heart, "and its recitation. So when We have recited it, follow its recitation" [Qiyamah 75:17–18], meaning when We send it down, listen, "Then upon Us is its clarification" [Qiyamah 75:19], meaning it is upon Us to make it clear through your tongue.He said that after this, whenever Jibreel came to him, he would remain silent and listen, and when Jibreel departed, he would recite it just as Allah had promised him.

حدثنا قتيبة بن سعيد حدثنا جرير عن موسى بن أبي عائشة

عن سعيد بن جبير

عن ابن عباس رضي الله عنهما في قوله {لا تحرك به لسانك لتعجل به} قال كان رسول الله ﷺ إذا نزل جبريل بالوحي وكان مما يحرك به لسانه وشفتيه فيشتد عليه وكان يعرف منه فأنزل الله الآية التي في لا أقسم بيوم القيامة {لا تحرك به لسانك لتعجل به إن علينا جمعه} فإن علينا أن نجمعه في صدرك {وقرآنه فإذا قرأناه فاتبع قرآنه} فإذا أنزلناه فاستمع {ثم إن علينا بيانه} قال إن علينا أن نبينه بلسانك قال وكان إذا أتاه جبريل أطرق فإذا ذهب قرأه كما وعده الله