And from him, from al-Hasan, from Safwan, from Ibn Muskan, from al-Halabi, who said:
I (narrator) asked Abu Abdillah عليه السلام, peace be upon him: “May the fasting person use the tooth-stick (siwak) with water and with the moist stick, whose taste he finds?” Imam عليه السلام said: “There is no harm in it.”
Ali Akbar al-Ghaffari
Tahdhīb al-Aḥkām fī Sharḥ al-Muqniʿah, vol. 4, p. 332