Musnad Ahmad 850:9

Yazid ibn Harun narrated to us, Hisham informed us, from al-Hasan, from Abd al-Rahman ibn Samurah, from the Prophet, peace and blessings of Allah be upon him, who said: "Do not swear by your fathers, nor by the *tawaghit* (idols/false deities)." And Yazid said: *al-tawaghi*.