مُوَطَّأُ مَالِكٍ
Muwatta Malik 145
Purity
وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ أَبِي الزِّنَادِ، عَنِ الأَعْرَجِ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ لَوْلاَ أَنْ أَشُقَّ عَلَى أُمَّتِي لأَمَرْتُهُمْ بِالسِّوَاكِ .
Yahya related to me from Malik from Abu'z Zinad from al-Araj from Abu Hurayra that the Messenger of Allah, (ﷺ), said, "Were it not that I would be overburdening my community I would have ordered them to use a tooth-stick."
Arabic/English book reference: Book 2, Hadith 116