Hashaym bin Bashayr bin al-Qasim هشيم بن بشير بن القاسم · Fasting (Kitab Al-Siyam)

I saw Ibn Umar holding his beard with his hand and cutting what exceeded the handful of it. He (Ibn Umar) said that the Prophet (ﷺ) said when he broke his fast: Thirst has gone, the arteries are moist, and the reward is sure, if Allah wills.

'Ashurah was a day on which we used to fast in pre-Islamic days. When (fasting of) Ramadan was prescribed, the Messenger of Allah (ﷺ) said: This is one of the days of Allah ; he who wishes may fast on it.