(8) The Book of Virtues
كتاب الفضائل
(215) Chapter: The Excellence of using Miswak (Tooth-Stick)
(215) - باب فضل السواك وخصال الفطرة‏:‏
Riyad as-Salihin 1198 
'Aishah (may Allah be pleased with her) reported:
We used to prepare for the Messenger of Allah (ﷺ) a Miswak (tooth-stick) and the water for making Wudu'. Whenever Allah wished to awaken him from sleep at night, he (ﷺ) would brush his teeth with Miswak, make Wudu', and perform Salat.

[Muslim].

وعن عائشة رضي الله عنها، قالت‏:‏ كنا نعد لرسول الله، سواكه وطهوره، فيبعثه الله ما شاء أن يبعثه من الليل، فيتسوك ويتوضأ ويصلي‏.‏ ‏(‏‏(‏رواه مسلم‏)‏‏)‏‏.‏
Reference : Riyad as-Salihin 1198
In-book reference : Book 8, Hadith 208