Abdullah bin Amir narrates from his father: I have seen the Prophet Muhammad (peace be upon him) using the miswak while fasting countless times.
Hadith Referenceمسند الحميدي / 141
Hadith Gradingمحدثین:إسناده ضعيف
Hadith Takhrij«إسناده ضعيف ، وأبو يعلى الموصلي فى ”مسنده“ :7193، وأحمد فى ”مسنده“ ، برقم: 15918»
Explanation & Benefits
Shaykh Muhammad Ibrahim bin Basheer
Benefit: Using the miswak (tooth-stick) while fasting is permissible. A fasting person may use the miswak at any part of the day. Even though this narration is weak.
Source: Musnad al-Humaydi: Commentary by Muhammad Ibrahim bin Bashir, Page: 141