That he asked Sa`id bin Jubair regarding (the statement of Allah). 'Move not your tongue concerning (the Qur'an) to make haste therewith.' He said, "Ibn `Abbas said that the Prophet (ﷺ) used to move his lips when the Divine Inspiration was being revealed to him. So the Prophet (ﷺ) was ordered not to move his tongue, which he used to do, lest some words should escape his memory. 'It is for Us to collect it' means, We will collect it in your chest;' and its recitation' means, We will make you recite it. 'But when We recite it (i.e. when it is revealed to you), follow its recital; it is for Us to explain it and make it clear,' (i.e. We will explain it through your tongue).
Reported by Al-Bukhari (No. 4928, 4929, 5044) and Muslim (No. 448a).
Ibn ‘Abbās (may Allah be pleased with him) commented about the verse: {Move not your tongue with it, [O Muhammad], to hasten with recitation of the Qur'an} [Sūrat al-Qiyāmah: 16], saying: "The Prophet (may Allah's peace and blessings be upon him) used to experience hardship while the revelation was…
يُعَالِجُ مِنَ التَّنْزِيلِ شِدَّةً، وَكَانَ يُحَرِّكُ شَفَتَيْهِ ـ فَقَالَ لِي ابْنُ عَبَّاسٍ أُحَرِّكُهُمَا لَكَ كَمَا كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم يُحَرِّكُهُمَا فَقَالَ سَعِيدٌ أَنَا أُحَرِّكُهُمَا كَمَا…