Musnad Ahmad 648:15

'Affan narrated to us, Hammad narrated to us, 'Ali bin Zayd narrated to us, from Salamah bin Muhammad bin 'Ammar bin Yasir, from 'Ammar bin Yasir, that the Messenger of Allah (ﷺ) said: "Indeed, from the *fitrah* (natural disposition), or the *fitrah*, are: rinsing the mouth, sniffing water into the nose, trimming the mustache, using the *siwak* (tooth stick), clipping the nails, washing the knuckles, plucking the underarm hair, shaving the pubic area, circumcision, and washing with water (after urination)."