Musnad Abu Ya'la al-Mawsili 148:66

Sufyan ibn Waki' ibn al-Jarrah narrated to us, my father narrated to us, from Uthman ibn Sa'd, from Anas ibn Malik, who said: When the Prophet, peace and blessings of Allah be upon him, would travel and stop at a place, and then intended to depart, he would bid farewell to the place with two rak'ahs.