The Book of Fasting
13/38. Chapter:
The virtue of fasting Muharram
Sahih Muslim
حَدَّثَنِي قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا أَبُو عَوَانَةَ، عَنْ أَبِي بِشْرٍ، عَنْ حُمَيْدِ بْنِ عَبْدِ الرَّحْمَنِ، الْحِمْيَرِيِّ عَنْ أَبِي هُرَيْرَةَ، - رضى الله عنه - قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " أَفْضَلُ الصِّيَامِ بَعْدَ رَمَضَانَ شَهْرُ اللَّهِ الْمُحَرَّمُ وَأَفْضَلُ الصَّلاَةِ بَعْدَ الْفَرِيضَةِ صَلاَةُ اللَّيْلِ " .
Abu Haraira (Allah be pleased with him) reported Allah's Messenger (ﷺ) as saying: The most excellent fast after Ramadan is God's month. al-Muharram, and the most excellent prayer after what is prescribed is prayer during the night.
Reference : Sahih Muslim 1163aIn-book reference : Book 13, Hadith 261USC-MSA web (English) reference : Book 6, Hadith 2611