It was narrated from Abu Mujibah Al-Bahili that his father or, his paternal uncle, said:
“I came to the Prophet ﷺ and said: ‘O Prophet of Allah, I am the man who came to you last year.’ He said: ‘Why do I see your body so thin (and weak)?’ He said: ‘O Messenger of Allah! I do not eat during the day; I only eat at night.’ He said: ‘Who commanded you to punish yourself?’ I said: ‘O Messenger of Allah! I am strong enough.’ He said: ‘Fast the month of patience* and one day after it.’ I said: ‘I am strong enough (to do more).’ He said: ‘Fast the month of patience and two days after it.’ I said: ‘I am strong enough (to do more).’ He said: ‘Fast the month of patience and three days after it, and fast the sacred months.’”

حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا وَكِيعٌ، عَنْ سُفْيَانَ، عَنِ الْجُرَيْرِيِّ، عَنْ أَبِي السَّلِيلِ، عَنْ أَبِي مُجِيبَةَ الْبَاهِلِيِّ، عَنْ أَبِيهِ، أَوْ عَنْ عَمِّهِ، قَالَ أَتَيْتُ النَّبِيَّ ـ ﷺ ـ فَقُلْتُ يَا نَبِيَّ اللَّهِ أَنَا الرَّجُلُ الَّذِي أَتَيْتُكَ عَامَ الأَوَّلِ . قَالَ " فَمَا لِي أَرَى جِسْمَكَ نَاحِلاً " . قَالَ يَا رَسُولَ اللَّهِ مَا أَكَلْتُ طَعَامًا بِالنَّهَارِ مَا أَكَلْتُهُ إِلاَّ بِاللَّيْلِ . قَالَ " مَنْ أَمَرَكَ أَنْ تُعَذِّبَ نَفْسَكَ " . قُلْتُ يَا رَسُولَ اللَّهِ إِنِّي أَقْوَى . قَالَ " صُمْ شَهْرَ الصَّبْرِ وَيَوْمًا بَعْدَهُ . قُلْتُ إِنِّي أَقْوَى . قَالَ " صُمْ شَهْرَ الصَّبْرِ وَيَوْمَيْنِ بَعْدَهُ " . قُلْتُ إِنِّي أَقْوَى . قَالَ " صُمْ شَهْرَ الصَّبْرِ وَثَلاَثَةَ أَيَّامٍ بَعْدَهُ وَصُمْ أَشْهُرَ الْحُرُمِ " .