Musnad Ahmad 1621

It was narrated from Mus"ab bin Sa"d bin Abi Waqqas, from his father, that he swore by al-Laf and al-"Uzza, and his companions said to him: You have said something unseemly. So he went to the Prophet (ﷺ) and said: I am newly Muslim, and I swore an oath by al-Lat and al‘Uzza. The Prophet (ﷺ) said to him: "Say La ilaha illallah wahdahu (there is no god but Allah alone) three times, and spit dryly to your left three times, and seek refuge with Allah from the Shaitan, and do not do it again."