Abu Naufal bin Abu Aqrab has narrated on the authority of his father that he asked the Prophet (ﷺ) about (voluntary) fasts. He said,"observe one fast every month." He submitted, "May my father and mother be ransomed to you, permit me to keep more. "The Prophet (ﷺ) repeated (in anger) what he had said, "permit me to keep more, permit me to keep more.” He then added," keep two fasts every month". But, Abu Nawafal’s father again requested, "May my parents be ransomed to you, allow me to keep more because I find myself able (to observe more), I find myself able, I find myself able." He then maintained silence and it seemed that he would not give permission any more until he said," keep three fasts every month."

حَدَّثَنَا عَبْدُ اللهِ بْنُ أَبِي بَكْرٍ، وَمُسْلِمٌ نَحْوَهُ، قَالاَ: حَدَّثَنَا الأَسْوَدُ بْنُ شَيْبَانَ، عَنْ أَبِي نَوْفَلِ بْنِ أَبِي عَقْرَبَ، أَنَّ أَبَاهُ سَأَلَ النَّبِيَّ ﷺ عَنِ الصَّوْمِ، فَقَالَ: صُمْ يَوْمًا مِنْ كُلِّ شَهْرٍ، قُلْتُ: بِأَبِي أَنْتَ وَأُمِّي، زِدْنِي، قَالَ: زِدْنِي، زِدْنِي، صُمْ يَوْمَيْنِ مِنْ كُلِّ شَهْرٍ، قُلْتُ: بِأَبِي أَنْتَ وَأُمِّي، زِدْنِي، فَإِنِّي أَجِدُنِي قَوِيًّا، فَقَالَ: إِنِّي أَجِدُنِي قَوِيًّا، إِنِّي أَجِدُنِي قَوِيًّا، فَأَفْحَمَ، حَتَّى ظَنَنْتُ أَنَّهُ لَنْ يَزِيدَنِي، ثُمَّ قَالَ: صُمْ ثَلاَثًا مِنْ كُلِّ شَهْرٍ.