Musannaf Ibn Abi Shayba 11:186

It was narrated to us by ‘Affan, from Sulayman ibn Kathir, who said: Ibn Shihab narrated to me, from ‘Ata’ ibn Yazid, from Abu Sa’id al-Khudri, who said: It was said, "O Messenger of Allah, which of the believers is best?" He said, "A believer who strives in the way of Allah with his self and his wealth, and a believer who isolates himself in a mountain pass—or he said, a ravine—sparing the people from his evil."