Musnad Abu Ya'la al-Mawsili 117:173

Shayban narrated to us, Hammad narrated to us, from Thabit, from Anas, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "When I was ascended to the seventh heaven, I was with Ibrahim, his back leaning against the Frequented House (al-Bayt al-Ma'mur). And behold, seventy thousand angels enter it every day, and they do not return to it."