Mishkat al-Masabih 7 Fasting كتاب الصوم 83

وَعَنِ ابْنِ عَبَّاسٍ قَالَ: مَا رَأَيْتُ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَتَحَرَّى صِيَامَ يَوْمٍ فَضَّلَهُ عَلَى غَيْرِهِ إِلَّا هَذَا الْيَوْمَ: يَوْمَ عَاشُورَاءَ وَهَذَا الشَّهْرُ يَعْنِي شَهْرَ رَمَضَان

Ibn ‘Abbas said, “I never saw the Prophet 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.” *The 10th of Muharram. (Bukhari and Muslim.)