Mishkat al-Masabih 3 Purification كتاب الطهارة 87

وَعَن شُرَيْح بن هَانِئ قَالَ: سَأَلْتُ عَائِشَةَ: بِأَيِّ شَيْءٍ كَانَ يَبْدَأُ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ إِذَا دخل بَيته؟ قَالَت: بِالسِّوَاكِ. رَوَاهُ مُسلم

Shuraih b. Hani’ said that he asked ‘A’isha what God’s messenger did first when he entered his house, and she replied that he used the tooth-stick. Muslim transmitted it.