Sunan Abu Dawood, Chapter: Purification (Kitab Al-Taharah)

I heard the Apostle of Allah (peace_be_upon_him) 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.