(9) باب مَا يَجُوزُ مِنَ اللَّوْ
Narrated Abu Huraira:
Allah's Messenger (ﷺ) said, "Were I not afraid that it would be hard on my followers, I would order them to use the siwak (as obligatory, for cleaning the teeth).
Reference: Sahih al-Bukhari 7240
In-book reference: Book 94, Hadith 15
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 9, Book 90, Hadith 346