Musannaf Ibn Abi Shayba 1:2049

Sharik narrated to us, from Layth, from Mujahid, who said: "Six are from the natural disposition (fitra) of Ibrahim: trimming the mustache, using the tooth stick (siwak), parting the hair, clipping the nails, cleaning with water after relieving oneself (istinja), and shaving the pubic hair." He said: "Three are on the head and three are on the body."