Abu Dawud Book 1, Hadith Number 47.

Chapter : The toothstick.

Narated By Zayd ibn Khalid al-Juhani : I heard the Apostle of Allah (PBUH) say: Were it not hard on my ummah, I would order them to use the tooth-stick at the time of every prayer. AbuSalamah said: Zayd ibn Khalid used to attend the prayers in the mosque with his tooth-stick on his ear where a clerk carries a pen, and whenever he got up for prayer he used it.