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