Sahih Bukhari: Hadith 7252

Sa`id bin Jubair reported from Ibn `Abbas (regarding the explanation of the Verse: 'Do not move your tongue concerning (the Qur'an) to make haste therewith) . He said, "The Prophet (ﷺ) used to undergo great difficulty in receiving the Divine Inspiration and used to move his lips.' Ibn `Abbas said (to Sa`id), "I move them (my lips) as Allah's Messenger (ﷺ) used to move his lips." And Sa`id said (to me), "I move my lips as I saw Ibn `Abbas moving his lips," and then he moved his lips. So Allah revealed:-- '(O Muhammad!) Do not move your tongue concerning (the Qur'an) to make haste therewith. It is for Us to collect it and give you (O Muhammad) the ability to recite it. (i.e., to collect it in your chest and then you recite it).' (75:16-17) But when We have recited it, to you (O Muhammad through Gabriel) then follow you its recital.' (75:18) This means, "You should listen to it and keep quiet and then it is upon Us to make you recite it." The narrator added, "So Allah's Messenger (ﷺ) used to listen whenever Gabriel came to him, and when Gabriel left, the Prophet (ﷺ) would recite the Qur'an as Gabriel had recited it to him."