Sahih Muslim 448 b
Ibn Abbas reported with regard to the words:
" Do not move thy tongue there with to make haste," that the Messenger of Allah (ﷺ) felt it hard and he moved his lips. Ibn 'Abbas said to me (Sa'id b. Jubair): I move them just as the Messenger of Allah (ﷺ) moved them. Then said Sa'id: I move them just as Ibn 'Abbas moved them, and he moved his lips. Allah, the Exalted, revealed this:" Do not move your tongue therewith to make haste. It is with US that its collection rests and its recital" (al-Qur'an, ixxv. 16). He said: Its preservation in your heart and then your recital. So when We recite it, follow its recital. He said: Listen to it, and be silent and then it rests with Us that you recite it. So when Gabriel came to the Messenger of Allah (ﷺ), he listened to him attentively, and when Gabriel went away, the Messenger of Allah (ﷺ) recited as he (Gabriel) had recited it.
حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا أَبُو عَوَانَةَ، عَنْ مُوسَى بْنِ أَبِي عَائِشَةَ، عَنْ سَعِيدِ بْنِ جُبَيْرٍ، عَنِ ابْنِ عَبَّاسٍ، فِي قَوْلِهِ ‏{‏ لاَ تُحَرِّكْ بِهِ لِسَانَكَ لِتَعْجَلَ بِهِ‏}‏ قَالَ كَانَ النَّبِيُّ صلى الله عليه وسلم يُعَالِجُ مِنَ التَّنْزِيلِ شِدَّةً كَانَ يُحَرِّكُ شَفَتَيْهِ - فَقَالَ لِيَ ابْنُ عَبَّاسٍ أَنَا أُحَرِّكُهُمَا كَمَا كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم يُحَرِّكُهُمَا ‏.‏ فَقَالَ سَعِيدٌ أَنَا أُحَرِّكُهُمَا كَمَا كَانَ ابْنُ عَبَّاسٍ يُحَرِّكُهُمَا ‏.‏ فَحَرَّكَ شَفَتَيْهِ - فَأَنْزَلَ اللَّهُ تَعَالَى ‏{‏ لاَ تُحَرِّكْ بِهِ لِسَانَكَ لِتَعْجَلَ بِهِ * إِنَّ عَلَيْنَا جَمْعَهُ وَقُرْآنَهُ‏}‏ قَالَ جَمْعَهُ فِي صَدْرِكَ ثُمَّ تَقْرَأُهُ ‏{‏ فَإِذَا قَرَأْنَاهُ فَاتَّبِعْ قُرْآنَهُ‏}‏ قَالَ فَاسْتَمِعْ وَأَنْصِتْ ثُمَّ إِنَّ عَلَيْنَا أَنْ تَقْرَأَهُ قَالَ فَكَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم إِذَا أَتَاهُ جِبْرِيلُ اسْتَمَعَ فَإِذَا انْطَلَقَ جِبْرِيلُ قَرَأَهُ النَّبِيُّ صلى الله عليه وسلم كَمَا أَقْرَأَهُ ‏.‏