Question 391: Salamualekum members. Please what is the view of ahlulbat on chewing stick (miswak) whiles fasting?
Answer 391: One of the things which is considered as makru for a person observing Fast is to clean his teeth with a wet toothbrush.
If a person, who is fasting, takes the tooth brush (Miswak) out of his mouth and then puts it back into his mouth, swallowing its liquid, his fast will be void, unless the moisture in the tooth brush mixes up with the saliva in such a way that it may no longer be called an external wetness.
When one rinses his mouth with water because it has dried due to thirst or to get rid of a bad smell of mouth and the water uncontrollably goes down one’s throat and one has already known it that if he\she does so the water will go down his\her throat, qadha has to be given.
A fast is not invalidated by swallowing the saliva which has gathered in the mouth, even if it has gathered due to recalling something. Likewise, according to the stronger opinion, (a fast is not invalidated) by swallowing the phlegm which has not yet reached the cavity of mouth, without there being any difference whether it has come down from the head or has emerged from the chest (or lungs). As regards the phlegm which has reached the cavity of mouth, caution must not be given up by abstaining from swallowing it. If the phlegm has come out of the mouth, and then a person swallows it, his fast shall thereby be rendered void. The same rule applies to saliva. Rather, (the same rule shall apply) if there is a pebble in the mouth of a person, and he takes it out, and there is some saliva on it, then the person puts it again into his mouth and swallows it. (The same rule shall apply), if a tailor wets a thread by his saliva, then puts it back into his mouth, and swallows it along with the moisture on it. (The same rule shall apply), if a person uses the tooth brush, and it comes out wet with saliva, and then he puts its back into his mouth and swallows the moisture etc., on it, and his fast shall be rendered void.
Of course, if the moisture on the tooth brush is mixed up with his saliva in a way that it may not be said that he has swallowed his saliva with something other in it, there shall be no harm. The same rule applies to tasting broth, chewing the food or the amount of water left after rinsing. Likewise, there is no harm in chewing the bark of a tree, according to the more valid opinion, even if its taste has remained in his saliva as long as it is not due to the scattering of its particles, even if they are absorbed in the mouth.
For further information in this regards, please refer to the following answers:
Index: Things from which a person keeping fast must abstain & Kaffarah (Expiation), answer 372.
Index: Studying in the month of Ramadhan is not a valid excuse to escape fasting, answer 572.
Index: Using Asthma Inhaler does not break the Fast, answer 575.
Index: Number of things which are disapproved (Makruh) for a person observing fast, answer 566.
Index: Fasting and prayers of a traveler who travel after Zuhr, answer 384.
Index: Qada Fast for a person reverted to Islam, answer 196.
Index: Rules of prayers and fasting performed without ghusl, answer 034.
Index: Fast in countries with long days, answer 106.
Index: Niyyat for Fasting: How to make intention to Fast Ramadan, answer 627.
 . Tawzih al-Masael (with annotation of Imam Khomeini (ra)), Vol. 1, Pg. 892, Q 1573; Ibid, Pgs. 895-942, Q 1582&1690; the Official website of Sayyid Sistani (ha), Rules concerning Fasting, occasions on which it is obligatory to observe the Qadha only; Tahrir al-Wasilah of Imam Khomeini, Vol. 1, Pg. 272.
 . Tahrir al-Wasilah of Imam Khomeini, Vol. 1, Chapter on Things Which Must Be Refrained in a Fast.