Musannaf Ibn Abi Shayba 3:2201

Abu Bakr narrated to us, he said: Ibn Fudayl narrated to us, from Khusayf, from Mujahid, who said: Ibn Umar, when he would enter a house and see a Mushaf (copy of the Quran) or something similar in the direction of the Qibla of the mosque, he would take it and cast it aside. And if it were to his right or to his left, he would leave it.