Musnad Ahmad 30:1167

Abu Amir narrated to us, Abdullah bin Ja'far narrated to us, from Uthman bin Muhammad, from al-Maqburi, from Abu Hurairah, from the Prophet, peace and blessings of Allah be upon him, who said: "There is no one who goes out—meaning from his house—except that at his door are two banners: a banner in the hand of an angel, and a banner in the hand of a devil. If he goes out for what Allah the Almighty loves, the angel follows him with his banner, and he remains under the banner of the angel until he returns to his house. And if he goes out for what angers Allah, the devil follows him with his banner, and he remains under the banner of the devil until he returns to his house."