Permissible things when fasting
It is a Sunnah to use the tooth-stick when fasting and it is permissible to use the tooth-stick at any time of the day
It is narrated on the authority of Hadhrat A’amir bin Rabee’a (May Allah be well pleased with him), he says that I have seen the Holy Prophet (Sallallahu alaihi wa sallam) use the tooth-stick so many times, that I cannot count them.
Tirmidhi and Abu Dawood have related this Hadith.
In the Hadith related by Tabarani, it is related on the authority of Hadhrat ‘Abdur Rahmaan bin Ghaman (May Allah shower His Mercy on him), he says: I asked Hadhrat Mua’adh bin Jabal (May Allah be well pleased with him): Can I use the tooth-stick when in a fasting state? He replied: Yes! (It is permissible to use the tooth-stick in a fasting state). Then I asked (him): (When fasting) At what time of the day should I use the tooth-stick? He replied: You can use it at whatever time of the day you want to, morning or evening (it is permissible to use the tooth-stick). I again said: Some people consider using the tooth-stick at evening (when fasting) as Undesirable and say (as proof) that the Holy Prophet (Sallallahu alaihi wa sallam) said: The mouth odor of the fasting person is more valuable than musk to Almighty Allah. (On hearing this) He (i.e. Hadhrat Mu’adh bin jabal (May Allah be well pleased with him)) said (with surprise): Subhaan Allaah! The Holy Prophet (Sallallahu alaihi wa sallam) ordered the Companions to use the tooth-stick (when fasting) and the Prophet himself knew that the mouth odor remains even one has used the tooth-stick. It cannot be expected of the Holy Prophet (Sallallahu alaihi wa sallam) that he would order the people to keep the odor of their mouths intact, when there is no benefit to it. In fact, there is harm in it. Of course, everyone has to bear this difficulty, for which there is no recourse (i.e. the even after using the tooth-stick, the mouth odor that emanates due to empty stomach cannot be escaped)
It is narrated on the authority of the mother of the believers Hadhrat ‘Aisha (May Allah be well pleased with her), she says that the Holy Prophet (Sallallahu alaihi wa sallam) said: One of the best things for a fasting person to do is to use the tooth-stick (while fasting at all hours of the day).
Ibn Majah, Daraqutni and Bayhaqui have related this Hadith.
[Excerpted from Noor ul Masabeeh, Vol. 4, Kitaab us Saum]