Hadith 2082
حَدَّثَنَا مُحَمَّدُ بْنُ بَشَّارٍ , حَدَّثَنَا يَحْيَى , حَدَّثَنَا عُبَيْدُ اللَّهِ , أَخْبَرَنِي نَافِعٌ , عَنِ ابْنِ عُمَرَ , قَالَ : كَانَ عَاشُورَاءُ يَوْمًا يَصُومُهُ أَهْلُ الْجَاهِلِيَّةِ , فَلَمَّا نَزَلَ رَمَضَانُ ، سُئِلَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ عَنْهُ , فَقَالَ : " يَوْمٌ مِنْ أَيَّامِ اللَّهِ , فَمَنْ شَاءَ صَامَهُ , وَمَنْ شَاءَ تَرَكَهُ "
Sayyiduna Ibn Umar (may Allah be pleased with them both) narrates that the people of the Age of Ignorance used to fast on the day of Ashura. Then, when the obligation of Ramadan was revealed, the Messenger of Allah (peace and blessings be upon him) was asked about it. He said: "It is one of the days of Allah, so whoever wishes may fast, and whoever wishes may leave it."
Hadith Reference صحيح ابن خزيمه / 2082
Hadith Takhrij صحيح بخاري