The Book of Purification
1/125. Chapter:
Rinsing The Mouth From Milk
Sunan an-Nasai
أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا اللَّيْثُ، عَنْ عُقَيْلٍ، عَنِ الزُّهْرِيِّ، عَنْ عُبَيْدِ اللَّهِ بْنِ عَبْدِ اللَّهِ، عَنِ ابْنِ عَبَّاسٍ، أَنَّ النَّبِيَّ صلى الله عليه وسلم شَرِبَ لَبَنًا ثُمَّ دَعَا بِمَاءٍ فَتَمَضْمَضَ ثُمَّ قَالَ " إِنَّ لَهُ دَسَمًا " .
The Apostle (ﷺ) took milk and then called for water and rinsed (his mouth) and said: It contains greasiness.
Reference : Sunan an-Nasa'i 187In-book reference : Book 1, Hadith 188English translation : Vol. 1, Book 1, Hadith 187