Musannaf Ibn Abi Shayba 1:633

Ibn ‘Ulayyah narrated to us, from Ayyub, from Abu Qilabah, from a man from Hudhayl—I think he mentioned that he had companionship [with the Prophet]—who said: "One should rinse the mouth after [consuming] milk, and one should not rinse the mouth after [consuming] dates."