Sayyiduna Ammar bin Yasir (may Allah be pleased with him) says: the Prophet (peace and blessings be upon him) said: "Ten things are part of the fitrah (natural disposition): rinsing the mouth, sniffing water into the nose, using the miswak, trimming the moustache, cutting the nails, plucking the armpit hair, shaving the pubic hair, washing the finger joints, sprinkling water, and circumcision."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 242