The Chapter of Siwak
Man Lā Yaḥḍuruh al-Faqīh|Volume 1|Book 1|Chapter 12
وَ تَرَكَ اَلصَّادِقُ عَلَيْهِ اَلسَّلاَمُ اَلسِّوَاكَ قَبْلَ أَنْ يُقْبَضَ بِسَنَتَيْنِ وَ ذَلِكَ أَنَّ أَسْنَانَهُ ضَعُفَتْ.
It is reported that Imam Jafar ibn Muhammad Al-Sadiq عليه السلام stopped using siwak two years before he passed away, as his teeth had weakened.
- Ṣaḥīḥ al-Faqīh