It was narrated that Umm Salamah, the wife of the Prophet, said:
"The Messenger of Allah said: 'If you drink milk, then rinse your mouths, for there is some greasiness in it.'" (IT)
English reference (IT): Vol. 1, Book 1, Hadith 499 (IT)
Arabic reference (IT): Book 1, Hadith 538 (IT)