Musannaf Ibn Abi Shayba 22:170

Zakariya narrated to us, he said: Atiyyah narrated to us, from Abu Sa’id al-Khudri, that the Prophet (peace be upon him) said: "Indeed, I am leaving among you the two weighty things, one of them is greater than the other: the Book of Allah, a rope extended from the heaven to the earth."