Musannaf Ibn Abi Shayba 22:291

Husayn ibn Ali narrated to us, from Za'idah, from 'Asim, from Zirr, who said: I said to Ubayy, "Indeed, Ibn Mas'ud does not write the two *Mu'awwidhatayn* (the two surahs of seeking refuge) in his *Mushaf* (copy of the Quran)." He said, "I asked the Prophet, peace and blessings of Allah be upon him, about them, and he said, 'It was said to me, so I said.' Therefore, we say as it was said to us."