Sahih Bukhari Volume 007, Book 072, Hadith Number 780.
Narrated By Nafi' : Ibn Umar said, The Prophet said, 'Do the opposite of what the pagans do. Keep the beards and cut the moustaches short.' Whenever Ibn 'Umar performed the Hajj or 'Umra, he used to hold his beard with his hand and cut whatever moustaches. Ibn Umar used to cut his moustache so short that the whiteness of his skin (above the upper lip) was visible, and he used to cut (the hair) between his moustaches and his beard.