حَدَّثَنَا مُسَدَّدٌ، حَدَّثَنَا يَحْيَى، عَنْ عُبَيْدِ اللَّهِ، قَالَ أَخْبَرَنِي نَافِعٌ، عَنِ ابْنِ عُمَرَ ـ رضى الله عنهما ـ قَالَ كَانَ عَاشُورَاءُ يَصُومُهُ أَهْلُ الْجَاهِلِيَّةِ، فَلَمَّا نَزَلَ رَمَضَانُ قَالَ ‏"‏ مَنْ شَاءَ صَامَهُ، وَمَنْ شَاءَ لَمْ يَصُمْهُ ‏"‏‏.‏
Translation
Narrated `Abdullah

That Al-Ash'ath entered upon him while he was eating. Al-Ash'ath said, "Today is 'Ashura." I said (to him), "Fasting had been observed (on such a day) before (the order of compulsory fasting in) Ramadan was revealed. But when (the order of fasting in) Ramadan was revealed, fasting (on 'Ashura') was given up, so come and eat."