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. (DE)
English reference (DE): Vol. 5, Book 44, Hadith 3329 (DE)
Arabic reference (DE): Book 47, Hadith 3648 (DE)