Musannaf Ibn Abi Shayba 22:295

Waki’ narrated to us, he said: Sufyan narrated to us, from al-A’mash, from Ibrahim, who said: I said to al-Aswad: "Are they from the Qur’an?" He said: "Yes," meaning the two *Mu’awwidhatayn* (Surah al-Falaq and Surah an-Nas).