Musannaf Ibn Abi Shayba 22:82

Abu Mu'awiyah narrated to us, from al-A'mash, from Shaqiq, who said: Abdullah said: "Maintain these copies of the Qur'an"—and he sometimes said: "the Qur'an"—"for it is more prone to escaping from the hearts of men than the camel is from its tether."