Is it permissible for a fasting person to use a siwak (tooth stick)?

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It is permissible for a fasting person to use a siwak. Ahmad affirmed this without issue. This is supported by the narration of 'Amir ibn Rabi'ah, who stated that he saw the Prophet (PBUH) using a siwak while fasting more times than he could count. Al-Tirmidhi classified this hadith as Hasan (good). Furthermore, Umar ibn Al-Khattab was observed using a withered stick for his siwak while fasting.