حَدَّثَنَا يَحْيَى عَنْ عُبَيْدِ اللَّهِ أَخْبَرَنِي نَافِعٌ عَنِ ابْنِ عُمَرَ قَالَ كَانَ يَوْمُ عَاشُورَاءَ يَوْمًا يَصُومُهُ أَهْلُ الْجَاهِلِيَّةِ فَلَمَّا نَزَلَ رَمَضَانُ سُئِلَ عَنْهُ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ هُوَ يَوْمٌ مِنْ أَيَّامِ اللَّهِ تَعَالَى مَنْ شَاءَ صَامَهُ وَمَنْ شَاءَ تَرَكَهُ
مسند امام احمد بن حنبل · Hadith 5203
It was narrated that Ibn 'Umar said: The day of 'Ashoora' was a day on which the people of the jahaliyyah used to fast . When (the command to fast) Ramadaan was revealed, the Messenger of Allah (PBUH) was asked about it and he said: Ashoora' is one of the days of Allah, so whoever wishes may omit it.”
Translated by Dr. Muhammad Muhsin Khan · Reviewed by Islamic University of Madinah · Published March 2020