Ja'far bin Iyas · Fasting (Kitab Al-Siyam)

The father or Uncle of Mujibah al-Bahiliyyah visited the Messenger of Allah (ﷺ). He then went away and came to him (again) after one year when his condition and appearance had changed. He said: Messenger of Allah, do you not recognize me? He asked: Who are you? He replied: I am al-Bahili who came to you last year. He said: What has changed you? You were looking well, then you were good in appearance? He said: I have only food…

'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.