Abu Dawud Book 28, Hadith Number 4186.
Chapter : Clipping the moustaches.
Narated By Abu Hurairah : The Prophet (PBUH) said: The inborn characteristics of man are five. Another versio says: Five things are characteristics pf man: circumcision, shaving the pubes, plucking the hair under the armpit, paring the nails and clipping the moustaches.