Musnad Abu Ya'la al-Mawsili 155:32

Amr al-Naqid narrated to us, Sufyan narrated to us, from al-Zuhri, from Sa'id, from Abu Hurayrah, who said: The Messenger of Allah (ﷺ) said: "Five are of the natural disposition (fitrah): circumcision, shaving the pubic hair, trimming the mustache, clipping the nails, and plucking the hair of the armpits."