حَدَّثَنَا قُتَيْبَةُ، حَدَّثَنَا أَبُو عَوَانَةَ، عَنْ أَبِي بِشْرٍ، عَنْ حُمَيْدِ بْنِ عَبْدِ الرَّحْمَنِ الْحِمْيَرِيِّ، عَنْ أَبِي هُرَيْرَةَ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ أَفْضَلُ الصِّيَامِ بَعْدَ صِيَامِ شَهْرِ رَمَضَانَ شَهْرُ اللَّهِ الْمُحَرَّمُ ‏"‏ ‏.‏ قَالَ أَبُو عِيسَى حَدِيثُ أَبِي هُرَيْرَةَ حَدِيثٌ حَسَنٌ ‏.‏
Translation
An-Nu'man bin Sa'd narrated

"A man asked Ali: "Which month do you order me to fast after the month of Ramadan?' He said to him, 'I have not heard anyone ask this except for a man whom I heard asking the Messenger of Allah while I was sitting with him. He said: "O Messenger of Allah! Which month do you order me to fast after the month of Ramadan?" He said: "If you will fast after the month of Ramadan, then fast Al-Muharram, for indeed it is Allah's month in which there is a day that Allah accepted the repentance of a people, and in which He accepts the repentance of other people."