JAMI AL-TIRMIDHI

Rinse mouth after drinking milk
  (89)

Sayyidina Ibn Abbas (RA) reported that the Prophet (SAW) drank milk and then asked for
water and rinsed his mouth. He said, “It is greasy”.
 
[Ahmed1951, 3051, Bukhari 211, 5609, Muslim 358, Abu Dawud  196, Nisai  187, Ibn e
Majah 498]