Musannaf Ibn Abi Shayba 28:1115

Ibn ‘Uyaynah narrated to us, from Ibn Abi Najih, who said: A man said in the presence of Mujahid: The Messenger of Allah (ﷺ) said: "The one is a devil, and the two are two devils." Mujahid said: The Messenger of Allah (ﷺ) sent Dihyah alone, and he sent ‘Abdullah and Khabbab as a detachment. However, ‘Umar said: "Be three in your travels, for if one dies, two will take charge of him. The one is a devil, and the two are two devils."