Al-Kāfi - Volume 4 > Disciplines to Maintain in the State of al-’Ihram
Hadith #6

6ـ عَلِيُّ بْنُ إِبْرَاهِيمَ عَنْ أَبِيهِ عَنِ ابْنِ أَبِي عُمَيْرٍ عَنْ مُعَاوِيَةَ قَالَ قُلْتُ لأَبِي عَبْدِ الله (عَلَيْهِ السَّلاَم) الْمُحْرِمُ يَسْتَاكُ قَالَ نَعَمْ قُلْتُ فَإِنْ أَدْمَى يَسْتَاكُ قَالَ نَعَمْ هُوَ مِنَ السُّنَّةِ وَرُوِيَ أَيْضاً لا يَسْتَدْمِي.

6. Ali ibn Ibrahim has narrated from his father from ibn abu ‘Umayr from Mu‘awiyah who has said the following: “I once asked abu ‘Abd Allah, ‘Alayhi al-Salam, about a man who is in the state of Ihram; if he can brush his teeth. He (the Imam) said, ‘Yes, it is of the Sunnah.’ It is also narrated that one must not make his teeth bleed.”