Volume 6, Book 60, Number 449:
Narrated Ibn Abbas:
The Prophet used to move his tongue when the divine Inspiration was being revealed to him.
(Sufyan, a subnarrator, demonstrated (how the Prophet used to move his lips) and added. “In order to
memorize it.” So Allah revealed: “Move not your tongue concerning (the Quran) to make haste there –
with.” (75.16)