"Ashura was a day that the Quraish used to fast during Jahiliyyah, and the Messenger of Allah used to fast it. But when (the fast of) Ramadan became obligatory, the Ramadan was the required and Ashura was left. So whoever wanted to, he fasted it, and whoever wanted to, he left it."  

كَانَ عَاشُورَاءُ يَوْمًا تَصُومُهُ قُرَيْشٌ فِي الْجَاهِلِيَّةِ وَكَانَ رَسُولُ اللَّهِ ﷺ يَصُومُهُ فَلَمَّا قَدِمَ الْمَدِينَةَ صَامَهُ وَأَمَرَ النَّاسَ بِصِيَامِهِ فَلَمَّا افْتُرِضَ رَمَضَانُ كَانَ رَمَضَانُ هُوَ الْفَرِيضَةَ وَتَرَكَ عَاشُورَاءَ فَمَنْ شَاءَ صَامَهُ وَمَنْ شَاءَ تَرَكَهُ وَفِي الْبَابِ عَنِ ابْنِ مَسْعُودٍ وَقَيْسِ بْنِ سَعْدٍ وَجَابِرِ بْنِ سَمُرَةَ وَابْنِ عُمَرَ وَمُعَاوِيَةَ