(19) باب صَوْمِ يَوْمِ عَاشُورَاءَ
'A'isha (Allah be pleased with her) reported that the Quraish used to fast on the day of Ashura during the pre-Islamic days. The Messenger of Allah (ﷺ) then commanded to fast on that day till (fasting) in Ramadan became obligatory. Then the Messenger of Allah (ﷺ) said:
He who wishes to fast should do so, and he who wishes to break it may do so. (ID)
Reference (ID): Sahih Muslim 1125 e (ID)
In-book reference (ID): Book 13, Hadith 147 (ID)
USC-MSA web (English) reference(deprecated numbering scheme): Book 6, Hadith 2503 (ID)