Hadith on Ashura: This is the day Moses fasted to thank Allah for saving his people

Ibn Abbas reported: The Messenger of Allah, peace and blessings be upon him, came to Medina and he found the Jews fasting the day of Ashura. The Prophet said, “What is this day you are fasting?” They said, “This is a great day in which Allah saved Moses and his people, and He drowned Pharaoh and his people. Moses fasted on it due to gratitude, so we also fast on it.” The Prophet said, “We have more right to it and we are closer to Moses than you.” The Prophet fasted the day of Ashura and he commanded fasting on it.

Source: Ṣaḥīḥ al-Bukhārī 3216, Ṣaḥīḥ Muslim 1130

Grade: Muttafaqun Alayhi (authenticity agreed upon) according to Al-Bukhari and Muslim

عَنْ ابْنِ عَبَّاسٍ رَضِيَ اللَّهُ عَنْهُمَا أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَدِمَ الْمَدِينَةَ فَوَجَدَ الْيَهُودَ صِيَامًا يَوْمَ عَاشُورَاءَ فَقَالَ لَهُمْ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ مَا هَذَا الْيَوْمُ الَّذِي تَصُومُونَهُ فَقَالُوا هَذَا يَوْمٌ عَظِيمٌ أَنْجَى اللَّهُ فِيهِ مُوسَى وَقَوْمَهُ وَغَرَّقَ فِرْعَوْنَ وَقَوْمَهُ فَصَامَهُ مُوسَى شُكْرًا فَنَحْنُ نَصُومُهُ فَقَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فَنَحْنُ أَحَقُّ وَأَوْلَى بِمُوسَى مِنْكُمْ فَصَامَهُ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ وَأَمَرَ بِصِيَامِهِ

3216 صحيح البخاري كتاب أحاديث الأنبياء باب قول الله تعالى وهل أتاك حديث موسى وكلم الله موسى تكليما

1130 صحيح مسلم كتاب الصيام باب صوم يوم عاشوراء