Ibn Abbas said:
"When the Quran was being revealed to the Messenger of Allah, he would move his tongue in attempt to memorize it. So Allah, Blessed is He and Most High, revealed: Move not your tongue concerning it to make haste therewith." He said: "So he would move his two lips." And Sufyan (a sub-narrator) would move his two lips. (ES)
English reference (ES): Vol. 5, Book 44, Hadith 3329 (ES)
Arabic reference (ES): Book 47, Hadith 3648 (ES)