Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī
muslim:1132a – Abū Bakr b. Abū Shaybah And ʿAmrw al-Nāqid > Sufyān > Abū Bakr > Ibn ʿUyaynah > ʿUbaydullāh b. Abū Yazīd > Ibn ʿAbbās Wasuʾil > Ṣiyām Yawm ʿĀshūrāʾ > Mā ʿAlimt

I do not know Messenger of Allah ﷺ singling out any day's fast and considering it more excellent than another, except this day (the day of Ashura) and this month, meaning the month of Ramadan.  

مسلم:١١٣٢a – حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ وَعَمْرٌو النَّاقِدُ جَمِيعًا عَنْ سُفْيَانَ قَالَ أَبُو بَكْرٍ حَدَّثَنَا ابْنُ عُيَيْنَةَ عَنْ عُبَيْدِ اللَّهِ بْنِ أَبِي يَزِيدَ سَمِعَ ابْنَ عَبَّاسٍ ؓ وَسُئِلَ عَنْ صِيَامِ يَوْمِ عَاشُورَاءَ فَقَالَ مَا عَلِمْتُ

أَنَّ رَسُولَ اللَّهِ ﷺ صَامَ يَوْمًا يَطْلُبُ فَضْلَهُ عَلَى الأَيَّامِ إِلاَّ هَذَا الْيَوْمَ وَلاَ شَهْرًا إِلاَّ هَذَا الشَّهْرَ يَعْنِي رَمَضَانَ