Musannaf Ibn Abi Shayba 7:146

Ubaydullah narrated to us, he said: Isra'il informed us, from Abu Ishaq, from Mus'ab bin Sa'd, from his father, that he said: I swore by Al-Lat and Al-'Uzza, so I came to the Prophet, peace and blessings of Allah be upon him, and said: "I have sworn by Al-Lat and Al-'Uzza." He said: "Say 'La ilaha illa Allah' (There is no god but Allah) three times, and spit to your left three times, and seek refuge in Allah from the Shaytan, then do not do it again."