'Abdul-Muhaimin bin 'Abbas bin Sahl bin Sa'd As-Sa'di narraed from his father, from his grandfather, that:The Messenger of Allah said: "Rinse your mouths after drinking milk, for it has some greasiness in it."
حَدَّثَنَا أَبُو مُصْعَبٍ، حَدَّثَنَا عَبْدُ الْمُهَيْمِنِ بْنُ عَبَّاسِ بْنِ سَهْلِ بْنِ سَعْدٍ السَّاعِدِيُّ، عَنْ أَبِيهِ، عَنْ جَدِّهِ، أَنَّ رَسُولَ اللَّهِ ـ صلى الله عليه وسلم ـ قَالَ " مَضْمِضُوا مِنَ اللَّبَنِ فَإِنَّ لَهُ دَسَمًا " .
IbnMaja
The Book of Purification and its Sunnah • Hadith 500