Musnad Abu Ya'la al-Mawsili 156:5

Wahb ibn Baqiyyah al-Wasiti narrated to us, Khalid narrated to us, from Yunus, from al-Hasan, from a man from Banu Sulayt, who said: I was in a piece of land of mine, and I saw a gathering. I said, "What is this?" They said, "The Messenger of Allah (may Allah bless him and grant him peace) is admonishing his companions." So I inserted my head between the people, and behold, the Prophet (may Allah bless him and grant him peace) was saying: "The Muslim is the brother of the Muslim," three times. "He does not wrong him, and he does not forsake him. Piety is here," and he gestured with his hand toward his chest.