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muslim:1127dMuḥammad b. Ḥātim > Isḥāq b. Manṣūr > Isrāʾīl > Manṣūr > Ibrāhīm > ʿAlqamah

Abu Abd al-Rahman, it is the day of 'Ashura (and you are eating). Upon this he said: Fast was observed on (this day) before the (fasting) in Ramadan was made obligatory, but when it was made obligatory, (fasting on the day of 'Ashura) was abandoned. So if you are not fasting, then take food.  

مسلم:١١٢٧dوَحَدَّثَنِي مُحَمَّدُ بْنُ حَاتِمٍ حَدَّثَنَا إِسْحَاقُ بْنُ مَنْصُورٍ حَدَّثَنَا إِسْرَائِيلُ عَنْ مَنْصُورٍ عَنْ إِبْرَاهِيمَ عَنْ عَلْقَمَةَ قَالَ دَخَلَ الأَشْعَثُ بْنُ قَيْسٍ عَلَى ابْنِ مَسْعُودٍ وَهُوَ يَأْكُلُ يَوْمَ عَاشُورَاءَ فَقَالَ

يَا أَبَا عَبْدِ الرَّحْمَنِ إِنَّ الْيَوْمَ يَوْمُ عَاشُورَاءَ فَقَالَ قَدْ كَانَ يُصَامُ قَبْلَ أَنْ يَنْزِلَ رَمَضَانُ فَلَمَّا نَزَلَ رَمَضَانُ تُرِكَ فَإِنْ كُنْتَ مُفْطِرًا فَاطْعَمْ  


See similar narrations below:

Collected by Aḥmad
ahmad:4024Yaʿlá And Ibn Abū Zāʾidah > al-Aʿmash > ʿUmārah > ʿAbd al-Raḥman b. Yazīd

[Machine] "Do you know the significance of the day of Ashura? Indeed, the Messenger of Allah ﷺ used to observe fasting on it before the month of Ramadan was made obligatory. However, when Ramadan was decreed as obligatory, the fasting of Ashura was abandoned."  

أحمد:٤٠٢٤حَدَّثَنَا يَعْلَى وَابْنُ أَبِي زَائِدَةَ قَالَا حَدَّثَنَا الْأَعْمَشُ عَنْ عُمَارَةَ عَنْ عَبْدِ الرَّحْمَنِ بْنِ يَزِيدَ قَالَ دَخَلَ الْأَشْعَثُ بْنُ قَيْسٍ عَلَى عَبْدِ اللهِ يَوْمَ عَاشُورَاءَ وَهُوَ يَتَغَدَّى فَقَالَ يَا أَبَا مُحَمَّدٍ ادْنُ لِلْغَدَاءِ قَالَ أَوَلَيْسَ الْيَوْمُ عَاشُورَاءَ؟ قَالَ

وَتَدْرِي مَا يَوْمُ عَاشُورَاءَ؟ إِنَّمَا كَانَ رَسُولُ اللهِ ﷺ يَصُومُهُ قَبْلَ أَنْ يَنْزِلَ رَمَضَانُ فَلَمَّا أُنْزِلَ رَمَضَانُ تُرِكَ