Answered by Shaykh Faraz Rabbani
I would appreciate if you could detail the fiqh of using the miswak in fasting. Does it break the fast if there is a taste of miswak left in the mouth? Does it break the fast if you wet it and then use it? Does it break the fast if a particle of wood remains in your mouth even after you try to get it out by spitting and later swallow it??
1. It remains a sunna to brush one’s teeth (siwak) throughout the day, even while fasting. (Maraqi)
2. The taste of the toothstick remaining does not invalidate one’s fast.
3. It is permitted to wet the toothstick or toothbrush before using it. It is best to spit out once when finished.
4. If you are certain that you swallowed a particle of wood, your fast is invalidated. If unsure, one resorts to one’s operating certainty: the fast is valid, for certainty is not lifted by mere doubt.
5. If any toothpaste or saliva changed by it gets swallowed, one’s fast is invalidated. It is best to avoid using toothpaste while fasting, unless one can do so without endangering one’s fast.