When the Prophet ﷺ on the day of 'Ashurah and commanded us to fast on it, they (i.e. Companions) said: Messenger of Allah, this is a day which is considered great by Jews and Christians ? The Messenger of Allah ﷺ said: When the next year comes, we shall fast on the 9th of Muharram. But the next year the Messenger of Allah ﷺ breathed his last.
سَمِعْتُ عَبْدَ اللَّهِ بْنَ عَبَّاسٍ يَقُولُ حِينَ صَامَ النَّبِيُّ ﷺ يَوْمَ عَاشُورَاءَ وَأَمَرَنَا بِصِيَامِهِ قَالُوا يَا رَسُولَ اللَّهِ إِنَّهُ يَوْمٌ تُعَظِّمُهُ الْيَهُودُ وَالنَّصَارَى فَقَالَ رَسُولُ اللَّهِ ﷺ فَإِذَا كَانَ الْعَامُ الْمُقْبِلُ صُمْنَا يَوْمَ التَّاسِعِ فَلَمْ يَأْتِ الْعَامُ الْمُقْبِلُ حَتَّى تُوُفِّيَ رَسُولُ اللَّهِ ﷺ