A man came to the Prophet ﷺ and said O Messenger of Allah, tell me of a month that I can fast after Ramadan. The Messenger of Allah ﷺ said: “If you want to fast a month after Ramadan, then fast al-Muharram, for it is the month of Allah and in it is a day on which Allah forgave people and will forgive more people.ʿ
أَتَى النَّبِيَّ ﷺ رَجُلٌ فَقَالَ يَا رَسُولَ اللهِ أَخْبِرْنِي بِشَهْرٍ أَصُومُهُ بَعْدَ رَمَضَانَ فَقَالَ رَسُولُ اللهِ ﷺ إِنْ كُنْتَ صَائِمًا شَهْرًا بَعْدَ رَمَضَانَ فَصُمِ الْمُحَرَّمَ فَإِنَّهُ شَهْرُ اللهِ وَفِيهِ يَوْمٌ تَابَ فِيهِ عَلَى قَوْمٍ وَيُتَابُ فِيهِ عَلَى آخَرِينَ