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.
darimi:1797Muḥammad b. Saʿīd > Muḥammad b. Fuḍayl > ʿAbd al-Raḥman b. Isḥāq > al-Nuʿmān b. Saʿd > Jāʾ a man > ʿAlī Fasaʾalah > Shahr Baʿd Shahr Ramaḍān Yaṣūmuh > Lah ʿAlī Mā Saʾalanī Aḥad > Hadhā Baʿd Idh

[Machine] I heard a man asking the Prophet ﷺ: "Which month should I fast after the month of Ramadan?" The Prophet ﷺ ordered him to fast during the month of Muharram and said, "Indeed, in it there is a day where Allah granted repentance to a nation, and He accepts the repentance of another nation."  

الدارمي:١٧٩٧حَدَّثَنَا مُحَمَّدُ بْنُ سَعِيدٍ حَدَّثَنَا مُحَمَّدُ بْنُ فُضَيْلٍ عَنْ عَبْدِ الرَّحْمَنِ بْنِ إِسْحاَقَ عَنْ النُّعْمَانِ بْنِ سَعْدٍ قَالَ جَاءَ رَجُلٌ إِلَى عَلِيٍّ فَسَأَلَهُ عَنْ شَهْرٍ بَعْدَ شَهْرِ رَمَضَانَ يَصُومُهُ فَقَالَ لَهُ عَلِيٌّ مَا سَأَلَنِي أَحَدٌ عَنْ هَذَا بَعْدَ إِذْ

سَمِعْتُ رَجُلًا سَأَلَ النَّبِيَّ ﷺ أَيُّ شَهْرٍ يَصُومُهُ مِنَ السَّنَةِ بَعْدَ شَهْرِ رَمَضَانَ؟ فَأَمَرَهُ بِصِيَامِ الْمُحَرَّمِ وَقَالَ «إِنَّ فِيهِ يَوْمًا تَابَ اللَّهُ عَلَى قَوْمٍ وَيَتُوبُ فِيهِ عَلَى قَوْمٍ»  


See similar narrations below:

Collected by Tirmidhī
tirmidhi:741ʿAlī b. Ḥujr > ʿAlī b. Mushir > ʿAbd al-Raḥman b. Isḥāq > al-Nuʿmān b. Saʿd > ʿAlī > Saʾalah a man > a Shahr Taʾmurunī > Aṣūm Baʿd Shahr Ramaḍān > Lah Mā > Aḥad Yasʾal

"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."  

Abū ʿĪsá said that this Ḥadīth is Ḥasan-Gharīb.
الترمذي:٧٤١حَدَّثَنَا عَلِيُّ بْنُ حُجْرٍ قَالَ أَخْبَرَنَا عَلِيُّ بْنُ مُسْهِرٍ عَنْ عَبْدِ الرَّحْمَنِ بْنِ إِسْحَاقَ عَنِ النُّعْمَانِ بْنِ سَعْدٍ عَنْ عَلِيٍّ

قَالَ سَأَلَهُ رَجُلٌ فَقَالَ أَىُّ شَهْرٍ تَأْمُرُنِي أَنْ أَصُومَ بَعْدَ شَهْرِ رَمَضَانَ قَالَ لَهُ مَا سَمِعْتُ أَحَدًا يَسْأَلُ عَنْ هَذَا إِلاَّ رَجُلاً سَمِعْتُهُ يَسْأَلُ رَسُولَ اللَّهِ ﷺ وَأَنَا قَاعِدٌ فَقَالَ يَا رَسُولَ اللَّهِ أَىُّ شَهْرٍ تَأْمُرُنِي أَنْ أَصُومَ بَعْدَ شَهْرِ رَمَضَانَ قَالَ إِنْ كُنْتَ صَائِمًا بَعْدَ شَهْرِ رَمَضَانَ فَصُمِ الْمُحَرَّمَ فَإِنَّهُ شَهْرُ اللَّهِ فِيهِ يَوْمٌ تَابَ اللَّهُ فِيهِ عَلَى قَوْمٍ وَيَتُوبُ فِيهِ عَلَى قَوْمٍ آخَرِينَ  

قَالَ أَبُو عِيسَى هَذَا حَدِيثٌ حَسَنٌ غَرِيبٌ