Musnad Abu Ya'la al-Mawsili 42:274

Zuhayr narrated to us, Abu ‘Amir narrated to us, from Zuhayr ibn Muhammad, from Zayd, from ‘Ata’ ibn Yasar, from Abu Sa’id, that the Prophet (peace and blessings of Allah be upon him) said: "Beware of sitting in the pathways." They said, "O Messenger of Allah, we have no choice regarding our sittings in which we converse." He said, "If you must sit, then give the path its right." They said, "And what is the right of the path?" He said, "Lowering the gaze, refraining from harm, returning the greeting, enjoining the good, and forbidding the evil."