Yazid bin Zari' يزيد بن زريع · Fasting (Kitab Al-Siyam)

We kept fast for twenty-nine days along with the Prophet (ﷺ) more often than we kept fast for thirty days.

I came to Ibn 'Abbas who was leaning against his sheet of cloth in the Sacred Mosque (al-Masjid al-Haram). I asked him about fasting on the day of 'Ashurah. He said: When you sight the moon of al-Muharram, count (the days). When the 9th of Muharram comes, fast from the morning. I said: Would Muhammad (ﷺ) observe this fast ? He replied: Thus Muhammad (ﷺ) used to fast.

The tradition mentioned above (No. 2468) has also been transmitted by Abdullah ibn Budayl through a different chain of narrators in a similar way. This version adds: While he (Umar) was observing i'tikaf (in the sacred mosque), the people uttered (loudly): "Allah is most great." He said: What is this, Abdullah? He said: These are the captives of the Hawazin whom the Messenger of Allah (ﷺ) has set free. He said: This slave-girl too? He sent her along with them.