Hudhayfah reported that whenever the Prophet ﷺ rose at night, he would clean his mouth thoroughly with the siwak.
كان النبي ﷺ إذا قام من الليل يشوص فاه بالسواك.
Bukhari reported it in wudu (245) and Muslim in purification (255). Both narrated it from Jareer, from Mansur, from Abu Waail, from Huzaifa, and he related the hadith.In the narration of Husayn bin Abdul-Rahman, from Abu Waail, in Muslim's version, "When he got up to perform tahajjud, he would rub his mouth with the siwak." Al-shaws means rubbing the teeth with the siwak sideways.