Musannaf Ibn Abi Shayba 1:2047

Ibn ‘Uyaynah narrated to us, from al-Zuhri, from Sa‘id, from Abu Hurayrah, from the Prophet (may Allah bless him and grant him peace), who said: "Five are of the *fitrah* (natural disposition): circumcision, shaving the pubic hair, clipping the nails, plucking the underarm hair, and trimming the mustache."