"Fast one day of each month." He asked him for more, saying: "May my father and mother be ransomed for you, I am able." He said: "Fast two days of each month." He said" May my father and mother be sacrificed for you, O Messenger of Allah, I am able." The Messenger of Allah said: "I am able, I am able." He did not want to increase it, but when I insisted, the Messenger of Allah said: "Fast three days of each month." (Sahih) The end of what the Shaikh had about fasting, all praise is due to Allah the Lord of the worlds. (Using translation from Nasāʾī 2434)   

أَنَّهُ سَأَلَ النَّبِيَّ ﷺ عَنِ الصَّوْمِ فَقَالَ صُمْ يَوْمًا مِنْ كُلِّ شَهْرٍ فَاسْتَزَادَهُ فَقَالَ بِأَبِي وَأُمِّي إِنِّي أَجِدُنِي أَقْوَى فَزِدْنِي فَقَالَ رَسُولُ اللهِ ﷺ إِنِّي أَجِدُنِي قَوِيًّا إِنِّي أَجِدُنِي قَوِيًّا فَمَا كَادَ أَنْ يَزِيدَهُ فَاسْتَزَادَهُ فَقَالَ صُمْ يَوْمَيْنِ مِنْ كُلِّ شَهْرٍ قَالَ بِأَبِي أَنْتَ وَأُمِّي يَا رَسُولَ اللهِ إِنِّي أَجِدُنِي قَوِيًّا فَقَالَ رَسُولُ اللهِ ﷺ إِنِّي أَجِدُنِي قَوِيًّا إِنِّي أَجِدُنِي قَوِيًّا ‍ فَمَا كَادَ أَنْ يَزِيدَهُ فَلَمَّا أَلْحَمَ عَلَيْهِ قَالَ رَسُولُ اللهِ ﷺ صُمْ ثَلَاثَةَ أَيَّامٍ مِنْ كُلِّ شَهْرٍ  

[Machine] I heard Abu Nawfal ibn Abi Aqrab saying, "My father asked the Messenger of Allah ﷺ about fasting. He said, 'Fast one day in every month.' My father said, 'O Messenger of Allah, increase me.' The Messenger of Allah ﷺ said, 'Increase me, increase me, and fast two days in every month.' He said, 'O Messenger of Allah, increase me, for I find myself strong.' The Messenger of Allah ﷺ said, 'I find myself strong, I find myself strong, I find myself strong.' He said, 'So I insisted until I thought he would not increase me.' He said, 'Then he said, 'Fast three days in every month.''  

سَمِعْتُ أَبَا نَوْفَلِ بْنَ أَبِي عَقْرَبٍ يَقُولُ سَأَلَ أَبِي رَسُولَ اللهِ ﷺ عَنِ الصَّوْمِ فَقَالَ صُمْ يَوْمًا مِنْ كُلِّ شَهْرٍ فَقَالَ يَا رَسُولَ اللهِ بِأَبِي وَأُمِّي زِدْنِي قَالَ يَقُولُ رَسُولُ اللهِ ﷺ زِدْنِي زِدْنِي صُمْ يَوْمَيْنِ مِنْ كُلِّ شَهْرٍ فَقَالَ يَا رَسُولَ اللهِ بِأَبِي وَأُمِّي زِدْنِي فَإِنِّي أَجِدُنِي قَوِيًّا قَالَ يَقُولُ رَسُولُ اللهِ ﷺ إِنِّي أَجِدُنِي قَوِيًّا إِنِّي أَجِدُنِي قَوِيًّا إِنِّي أَجِدُنِي قَوِيًّا قَالَ فَأَلْحَمَ أَيْ أَمْسَكَ حَتَّى ظَنَنْتُ أَنَّهُ لَنْ يَزِيدَنِي قَالَ ثُمَّ قَالَ صُمْ ثَلَاثَةَ أَيَّامٍ مِنْ كُلِّ شَهْرٍ