"Whenever the Messenger of Allah got up for prayer at night to pray Tahajjud (night optional prayer), he would clean his mouth with the tooth stick." (Using translation from Ibn Mājah 286)  

كَانَ رَسُولُ اللَّهِ ﷺ «إِذَا قَامَ إِلَى التَّهَجُّدِ يَشُوصُ فَاهُ بِالسِّوَاكِ»