Musnad Ahmad 1909

Ibn ‘Abbas said: When Qur"an was revealed to the Prophet (ﷺ), he would want to memorise it. Allah said: "Move not your tongue concerning (the Qur"an, O Muhammad (ﷺ) to make haste therewith. It is for Us to collect it and to give you (O Muhammad(ﷺ)) the ability to recite it (the Qur"an). And when We have recited it to you [O Muhammad (ﷺ) through Jibreel] then follow its (the Qur"an"s) recital” al-Qiyamah 75:16-18].