Sahih Muslim Book - 4, Hadith - 1004

و حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ وَأَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ وَإِسْحَقُ بْنُ إِبْرَاهِيمَ كُلُّهُمْ عَنْ جَرِيرٍ قَالَ أَبُو بَكْرٍ حَدَّثَنَا جَرِيرُ بْنُ عَبْدِ الْحَمِيدِ عَنْ مُوسَى بْنِ أَبِي عَائِشَةَ عَنْ سَعِيدِ بْنِ جُبَيْرٍ عَنْ ابْنِ عَبَّاسٍ فِي قَوْلِهِ عَزَّ وَجَلَّ { لَا تُحَرِّكْ بِهِ لِسَانَكَ } قَالَ كَانَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ إِذَا نَزَلَ عَلَيْهِ جِبْرِيلُ بِالْوَحْيِ كَانَ مِمَّا يُحَرِّكُ بِهِ لِسَانَهُ وَشَفَتَيْهِ فَيَشْتَدُّ عَلَيْهِ فَكَانَ ذَلِكَ يُعْرَفُ مِنْهُ فَأَنْزَلَ اللَّهُ تَعَالَى { لَا تُحَرِّكْ بِهِ لِسَانَكَ لِتَعْجَلَ بِهِ } أَخْذَهُ { إِنَّ عَلَيْنَا جَمْعَهُ وَقُرْآنَهُ } إِنَّ عَلَيْنَا أَنْ نَجْمَعَهُ فِي صَدْرِكَ وَقُرْآنَهُ فَتَقْرَؤُهُ { فَإِذَا قَرَأْنَاهُ فَاتَّبِعْ قُرْآنَهُ } قَالَ أَنْزَلْنَاهُ فَاسْتَمِعْ لَهُ { إِنَّ عَلَيْنَا بَيَانَهُ } أَنْ نُبَيِّنَهُ بِلِسَانِكَ فَكَانَ إِذَا أَتَاهُ جِبْرِيلُ أَطْرَقَ فَإِذَا ذَهَبَ قَرَأَهُ كَمَا وَعَدَهُ اللَّهُ.

It was narrated that Ibn 'Abbas said concerning Allah's saying: "Move not your tongue concerning it..." "When Jibril brought the Revelation down to him (i.e. the Prophet (s.a.w)), he would move his tongue and lips with it, which was visibly hard for him. Then Allah, the Most High revealed: "Move not your tongue concerning it to make haste therewith" meaning, in learning it. "It is for Us to collect it and to give you the ability to recite it " We will preserve it in your heart and enable you to recite it. "And when We have recited it to you, then follow its recitation" meaning: We have sent it down, so listen to it. "Then it is for Us to make it clear", meaning: We will explain it on your tongue. So when Jibril came to him, he kept silent, and when he departed, he recited it as Allah promised he would."