Abu Dawud Book 1, Hadith Number 52.

Chapter : Using toothstick is one of the characteristics of fitrah nature.

Narated By ‘Aisha, Ummul Mu’minin : The Apostle of Allah (PBUH) said: Ten are the acts according to fitrah (nature): clipping the moustache, letting the beard grow, using the tooth-stick, cutting the nails, washing the finger joints, plucking the hair under the arm-pits, shaving the pubes, and cleansing one’s private parts (after easing or urinating) with water. The narrator said: I have forgotten the tenth, but it may have been rinsing the mouth.