Musannaf Ibn Abi Shayba 38:135

Yahya ibn Adam narrated to us, he said: Abd al-Rahman ibn Humayd al-Ru'asi narrated to us, he said: Imran ibn Zabyan narrated to us, from Abu Yahya, he said: He heard a man from the Khawarij while he was praying the dawn prayer saying: "And it has already been revealed to you and to those before you that if you should associate [anything] with Allah, your work would surely become worthless, and you would surely be among the losers." He said: So he abandoned his surah that he was in. He said: And he recited: "So be patient. Indeed, the promise of Allah is truth. And let not those who have no certainty disquiet you."