رِيَاضُ الصَّالِحِينَ
Riyad as-Salihin 1252
The Book of Virtues
The Excellence of Observing Saum on the Day of 'Arafah, 'Ashura' and Tasu'a (i.e., 9th of Muharram)
وَعَنْ أَبِي قَتَادَةَ رَضِيَ اللَّه عَنْهُ أَنَّ رَسُولَ اَللَّهِ صَلَّى اللَّه عَلَيْهِ وَسَلَّمَ سئل عَنْ صِيَامِ يَوْمِ عَاشُورَاءَ فَقَالَ: يكفر السنة الماضية ((رَوَاهُ مُسْلِم)).
Abu Qatadah (May Allah be pleased with him) reported: The Messenger of Allah (ﷺ) was asked about observing As-Saum (the fast) on the tenth day of Muharram, and he replied, "It is an expiation for the sins of the preceding year." [Muslim].
Riyad as-Salihin, 1252