Sayyiduna Abu Hurayrah (may Allah be pleased with him) narrated that he (peace and blessings be upon him) said: "The fitrah is five things, or five things are part of the fitrah (he said one of the two): circumcision, using a razor (shaving the pubic hair), plucking the armpit hair, trimming the moustache and clipping the nails."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 686