I asked Ayesha, "What was the first thing the Prophet ﷺ would do when he entered his house?"She replied, "He would use the siwak."
أخبرنا علي بن خشرم قال حدثنا عيسى وهو ابن يونس عن مسعر
قلت لعائشة بأي شيء كان يبدأ النبي ﷺ إذا دخل بيته قالت بالسواك
Muslim also narrated it in the Book of Purification, Chapter on the Tooth-stick, hadith (253), from the hadith of Masaar, with the same wording. It is also found in Al-Kubra, hadith (7).