The Fasting Section · 69 – Those who say that fasting three days each month was on Mondays and Thursdays.
Hafsā (may Allah be pleased with her) related:
The Messenger of Allah (peace and blessings upon him) would fast three days each month, the first week on Mondays and Thursdays, and from another week on Monday.
Hüneydetü-l-Huzâî from her mother related:
I entered upon Ümmü Seleme. I asked her about fasting. She said:
The Messenger of Allah, peace and blessings be upon him, commanded me to fast three days each month. Those were the first days of fasting for me, Monday and Thursday.