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

on the authority of his father( Abu Musa al-Ashari) (according to the version of Musaddad): We came to the Apostle of Allah (peace_be_upon_him) to provide us with a mount, and found him using the tooth-stick, its one end being at his tongue (i.e. he was rinsing his mouth). According to the version of Sulaiman it goes: I entered upon the Prophet (peace_be_upon_him) who was using the tooth-stick and had placed it at one side of his tongue, producing a gurgling sound. Abu Dawud said: Musaddad said that the tradition was leangthy but he shortened it.