صَحِيحُ مُسْلِمٍ
Sahih Muslim 1133 a
The Book of Fasting
Which day should be fasted for 'Ashura?
وَحَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا وَكِيعُ بْنُ الْجَرَّاحِ، عَنْ حَاجِبِ بْنِ عُمَرَ، عَنِ الْحَكَمِ بْنِ الأَعْرَجِ، قَالَ انْتَهَيْتُ إِلَى ابْنِ عَبَّاسٍ - رضى الله عنهما - وَهُوَ مُتَوَسِّدٌ رِدَاءَهُ فِي زَمْزَمَ فَقُلْتُ لَهُ أَخْبِرْنِي عَنْ صَوْمِ عَاشُورَاءَ . فَقَالَ إِذَا رَأَيْتَ هِلاَلَ الْمُحَرَّمِ فَاعْدُدْ وَأَصْبِحْ يَوْمَ التَّاسِعِ صَائِمًا . قُلْتُ هَكَذَا كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم يَصُومُهُ قَالَ نَعَمْ .
Hakam b. al-'Araj reported: I went to Ibn 'Abbas (Allah be Pleased with both of them) and he was reclining using his mantle as a pillow near the fountain of Zamzam. I said to him: Tell me about fasting on Ashura. He said: When you see the new moon of Muharram then count the (days) and observe fast on the 9th. I said to him: Is it how the Messenger of Allah (ﷺ) observed the fast? He said: Yes.
Sahih Muslim, 1133 aSahihصحيح