The Prophet ﷺ drank some milk, then called for water and rinsed his mouth, saying, "It has greasiness to it."
حدثنا قتيبة حدثنا الليث عن عقيل عن الزهري عن عبيد الله بن عبد الله
أن النبي ﷺ شرب لبنا فدعا بماء فمضمض وقال إن له دسما
Agreed upon [by Bukhari and Muslim]. Bukhari reported it in the Book of Wudu, chapter "Should One Rinse the Mouth After Milk", hadith no. 211, and Muslim reported it in the Book of Menstruation, chapter "The Abrogation of Wudu for What the Fire Has Touched", hadith no. 358/95, both from Qutayba, through the same chain.On this topic, there are also narrations from Sahl bin Saad Saadi [Ibn Majah, no. 500] and Umm Salama [Ibn Majah, no. 499].