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.  

إِذَا رَأَيْتَ هِلاَلَ الْمُحَرَّمِ فَاعْدُدْ وَأَصْبِحْ يَوْمَ التَّاسِعِ صَائِمًا قُلْتُ هَكَذَا كَانَ رَسُولُ اللَّهِ ﷺ يَصُومُهُ قَالَ نَعَمْ  

I came to Ibn 'Abbas who was leaning against his sheet of cloth in the Sacred Mosque (al-Masjid al-Haram). I asked him about fasting on the day of 'Ashurah. He said: When you sight the moon of al-Muharram, count (the days). When the 9th of Muharram comes, fast from the morning. I said: Would Muhammad ﷺ observe this fast ? He replied: Thus Muhammad ﷺ used to fast.  

إِذَا رَأَيْتَ هِلاَلَ الْمُحَرَّمِ فَاعْدُدْ فَإِذَا كَانَ يَوْمُ التَّاسِعِ فَأَصْبِحْ صَائِمًا فَقُلْتُ كَذَا كَانَ مُحَمَّدٌ ﷺ يَصُومُ فَقَالَ كَذَلِكَ كَانَ مُحَمَّدٌ ﷺ يَصُومُ  

[Machine] "If you see the crescent of Muharram, then count. And when you reach its ninth day, then fast on that day. I asked, 'Was this how Muhammad ﷺ used to fast it?' He replied, 'Yes.'"  

إِذَا رَأَيْتَ هِلالَ الْمُحَرَّمِ فَاعْدُدْ فَإِذَا أَصْبَحْتَ مِنْ تَاسِعِهِ فَصُمْ ذَلِكَ الْيَوْمَ قُلْتُ أَهَكَذَا كَانَ يَصُومُهُ مُحَمَّدٌ ﷺ؟ قَالَ نَعَمْ  

[Machine] "When you see the crescent of the month of Muharram, then start preparing, and fast on the ninth day." He said, "I asked, 'Did Muhammad ﷺ used to observe this fast?' He replied, 'Yes.'  

إِذَا رَأَيْتَ هِلَالَ الْمُحَرَّمِ فَاعْدُدْ فَأَصْبِحْ مِنَ التَّاسِعَةِ صَائِمًا قَالَ قُلْتُ أَكَذَاكَ كَانَ يَصُومُهُ مُحَمَّدٌ عَلَيْهِ الصَّلَاةُ وَالسَّلَامُ ؟ قَالَ نَعَمْ  

[Machine] "If you see the crescent moon of Muharram, then prepare. And if you reach the ninth day, then fast it. I said, 'Did the Prophet Muhammad ﷺ used to fast on it?' He said, 'Yes.'"  

إِذَا رَأَيْتَ هِلالَ الْمُحَرَّمِ فَاعْدُدْ فَإِذَا أَصْبَحْتَ مِنْ تَاسِعَةٍ فَأَصْبِحْ مِنْهَا صَائِمًا قُلْتُ أَكَذَاكَ كَانَ يَصُومُهُ مُحَمَّدٌ ﷺ ؟ قَالَ نَعَمْ  

[Machine] "I approached Ibn Abbas while he was sitting beside his robe near Zamzam, and I sat beside him. What a wonderful companion he was! I asked him about Ashura. He sat upright and asked me, "Which aspect of it do you want to know?" I said, "I want to know about its fasting, which day do we fast?" He replied, "When you see the crescent moon of Muharram, then count and start fasting from the ninth day." I asked, "Did Muhammad ﷺ also fast in this manner?" He answered, "Yes.""  

انْتَهَيْتُ إِلَى ابْنِ عَبَّاسٍ وَهُوَ مُتَوَسِّدٌ رِدَاءَهُ عِنْدَ زَمْزَمَ فَجَلَسْتُ إِلَيْهِ وَنِعْمَ الْجَلِيسُ كَانَ فَسَأَلْتُهُ عَنْ عَاشُورَاءَ؟ فَاسْتَوَى جَالِسًا ثُمَّ قَالَ «عَنْ أَيِّ بَابِهِ تَسْأَلُ؟ » قَالَ قُلْتُ عَنْ صِيَامِهِ أَيَّ يَوْمٍ نَصُومُهُ؟ قَالَ «إِذَا رَأَيْتَ هِلَالَ الْمُحَرَّمِ فَاعْدُدْ ثُمَّ أَصْبِحْ مِنْ تَاسِعِهِ صَائِمًا» قُلْتُ أَكَذَلِكَ كَانَ يَصُومُ مُحَمَّدٌ ﷺ قَالَ «نَعَمْ»