Reference: Fataawa Ramadhaan – Volume 2, Page 491, Fatwa No. 440
al-Fataawa libni ‘Uthaymeen – Kitaab ad-Da’wah, Volume 1, Page 167
Question: What is the ruling concerning the one who fasts using a miswaak (tooth stick) after zawaal (when the sun is at its highest point and there is no shadow)?
Response: The use of the miswaak either before or after zawaal is a Sunnah as it is a Sunnah at other than these times. This is because the Hadeeth regarding the use of the miswaak is general and does not exempt the one who is fasting either before zawaal or after zawaal. The Prophet (sal-Allaahu ‘alayhi wa sallam) said:
«The miswaak is a purifier for the mouth, [and] much liked by the Lord, . . .».
Also, he (sal-Allaahu ‘alayhi wa sallam) said:
«If it were not that I feared inconvenience for my Ummah, I would have ordered them to use the miswaak before each prayer».