when the Messenger of Allah (may Allah's peace and blessings be upon him) used to get up at night, he would cleanse his mouth with the tooth-stick. [Sahih/Authentic] - [Al-Bukhari and Muslim

"«كان رسول الله -صلى الله عليه وسلم- إِذَا قَام من اللَّيل يُشُوصُ فَاهُ بِالسِّوَاك». [صحيح.] - [متفق عليه.]"