Sunan an-Nasa'i — The Book of Water — Hadith No: 331

It was narrated that Abu Musa said:"I came to the Messenger of Allah (ﷺ) when he was using the Siwak, and the end of the Siwak was on his toungue, and he was saying, "'A','a

Abdur-Rahman bin Abu 'Atiq said:"My father told me: 'I heard 'Aishah say, (narrating) from the Prophet (ﷺ): "Siwak is a means of purification for the mouth and is pleasing to the Lord

It was narrated from Al-Miqdam - Abu Shuraih - that his father said:"I said to 'Aishah: 'What did the Prophet (ﷺ) start with when he entered his house?' She said: 'The Siwak

It was narrated from Abu Hurairah that the Prophet (ﷺ) said:"The Fitrah are five: Circumcision, shaving the pubes, plucking the armpit hairs, clipping the nails and taking from the mustache