Yahya related to me from Malik from Yahya ibn Said that Said ibnal-Musayyub said, "Ibrahim, may Allah bless him and grant him peace,was the first to give hospitality to the guest and the first person tobe circumcised and the first person to trim the moustache and thefirst person to see grey hair. He said, 'O Lord! What is this?' Allahthe Blessed, the Exalted, said, 'It is dignity, Ibrahim.' He said,'Lord, increase me in dignity!' "Yahya said that he hadheard Malik say, "One takes from the moustache until the edge of thelip appears, that is the rim. One does not cut if off completely sothat one mutilates oneself."
USC-MSA web (English) reference: Book 49, Hadith 4
Arabic reference: Book 49, Hadith 1677