"The Messenger of Allah said: 'I have heard that you stand (in prayer) all night and fast all day.' I said: 'O Messenger of Allah, I only meant good by that.' He said: 'One who fasts every day of his life has not truly fasted. But I will tell you what fasting for a lifetime means: Three days of every month.' I said: 'O Messenger of Allah, I said: 'I am able to do more than that.' He said 'Observe the fast of Dawud, peace be upon him; he used to fast one day and not the next."' 'Ata said: "someone who heard him told me that Ibn 'Umar (said) that the Prophet said: 'Whoever fasts every day of his life, then he has not fasted." (Using translation from Nasāʾī 2397)   

قَالَ لِي رَسُولُ اللهِ ﷺ «إِنَّهُ بَلَغَنِي أَنَّكَ تَقُومُ اللَّيْلَ وَتَصُومُ النَّهَارَ؟» قُلْتُ يَا رَسُولَ اللهِ مَا أَرَدْتُ بِذَلِكَ إِلَّا الْخَيْرَ قَالَ «لَا صَامَ مَنْ صَامَ الْأَبَدَ وَلَكِنْ أَدُلُّكَ عَلَى صَوْمِ الدَّهْرِ ثَلَاثَةُ أَيَّامٍ مِنَ كُلِّ شَهْرٍ» قُلْتُ يَا رَسُولَ اللهِ إِنِّي أُطِيقُ أَفْضَلَ مِنْ ذَلِكَ قَالَ «فَصُمْ خَمْسَةَ أَيَّامٍ» قُلْتُ إِنِّي أُطِيقُ أَفْضَلَ مِنْ ذَلِكَ قَالَ «فَصُمْ عَشْرًا» قُلْتُ إِنِّي أُطِيقُ أَفْضَلَ مِنْ ذَلِكَ قَالَ «فَصُمْ صَوْمَ دَاوُدَ وَكَانَ يَصُومُ يَوْمًا وَيُفْطِرُ يَوْمًا»  

[Machine] Abu al-Abbas, a man from Sham who was a poet and known for his honesty, narrated to me that Abdullah ibn Amr said: The Messenger of Allah ﷺ said to me, "Indeed, you pray at night and fast during the day. No one can fast forever, but fast for three days each month." I asked, "Increase me." He said, "Fast for five days each month." I asked, "Increase me." He said, "The best fasting is the fasting of Dawood (David) who used to fast one day and break his fast on the next, and he never missed it when he met with others."  

حَدَّثَنِي أَبُو الْعَبَّاسِ وَكَانَ رَجُلًا مِنْ أَهْلِ الشَّامِ وَكَانَ شَاعِرًا وَكَانَ صَدُوقًا عَنْ عَبْدِ اللهِ بْنِ عَمْرٍو قَالَ قَالَ لِي رَسُولُ اللهِ ﷺ إنَّكَ تَقُومُ اللَّيْلَ وَتَصُومُ النَّهَارَ لَا صَامَ مَنْ صَامَ الْأَبَدَ صُمْ مَنْ كل شَّهْرِ ثَلَاثَةُ أَيَّامٍ قُلْتُ زِدني قال «صُمْ مَنْ كل شهر خَمْسَةَ أَيَّامٍ» قُلْتُ زِدني قَالَ «أَفْضَلُ الصِّيَامِ صَوْمَ دَاوُدَ يَصُومُ يَوْمًا وَيُفْطِرُ يَوْمًا وَلَا يَفِرَّ إِذَا لَاقَى»  

"The Messenger of Allah said to me: 'O 'Abdullah bin 'Amr, you fast all the time and you do stand (in prayer) at night, but if you do that your eyes will become sunken and you will become exhausted. There is no fast for one who fasts every day of his life. Fasting a lifetime means fasting three days each month, (Using translation from Nasāʾī 2399)  

قَالَ لِي رَسُولُ اللهِ ﷺ «يَا عَبْدَ اللهِ بْنَ عَمْرٍو إِنَّكَ تَصُومُ الدَّهْرَ وَتَقُومُ اللَّيْلَ وَإِنَّكَ إِذَا فَعَلْتَ ذَلِكَ هَجَمَتِ الْعَيْنُ وَنفهت لَهُ النَّفْسُ لَا صَامَ مَنْ صَامَ الْأَبَدَ صَوْمُ الدَّهْرِ ثَلَاثَةُ أَيَّامٍ مِنَ الشَّهْرِ صَوْمُ الدَّهْرِ كُلِّهِ» قُلْتُ إِنِّي أُطِيقُ أَكْثَرَ مِنْ ذَلِكَ قَالَ «صَوْمُ دَاوُدَ كَانَ يَصُومُ يَوْمًا وَيُفْطِرُ يَوْمًا وَلَا يَفِرُّ إِذَا لَاقَى»  

"The Messenger of Allah said to me: 'Read the Qur'an in a month.' I said: 'I am able to do more than that. ' And I kept asking him until he said: 'In five days.' And he said: 'Fast three days a month.' I said: 'I am able to do more than that.' And 'Observe thhe most beloved of fasting to Allah, the Mighty and Sublime, the fast one day and not the next." (Suahih). (Using translation from Nasāʾī 2400)  

قَالَ لِي رَسُولُ اللهِ ﷺ «اقْرَأِ الْقُرْآنَ فِي شَهْرٍ» قُلْتُ إِنِّي أُطِيقُ أَكْثَرَ مِنْ ذَلِكَ قَالَ فَلَمْ أَزَلْ أَطْلُبُ إِلَيْهِ حَتَّى قَالَ «فِي خَمْسَةِ أَيَّامٍ» وَقَالَ «صُمْ ثَلَاثَةَ أَيَّامٍ مِنَ الشَّهْرِ» قُلْتُ إِنِّي أُطِيقُ أَكْثَرَ مِنْ ذَلِكَ قَالَ فَلَمْ أَزَلْ أَطْلُبُ إِلَيْهِ حَتَّى قَالَ لِي «صُمْ أَحَبَّ الصِّيَامِ إِلَى اللهِ صَوْمَ دَاوُدَ كَانَ يَصُومُ يَوْمًا وَيُفْطِرُ يَوْمًا»  

"The Messenger of Allah heard that I was fasting continually and praying all night." Either he sent for him, or he happened to meet him and he said: "Have I not been told that you fast and never break your fast, and you pray all night? Do not do that, for do that, for your eyes should have a share, your self should have a share, and your family should have a share. Fast and break your fast; pray and sleep. Fast one day out of every ten, and your will have the reward of the other nine." He said: " I am able to do more than that, O Messenger of Allah." He said: "Observe the fast of Dawud then." " I said: 'How did Dawud fast, O Prophet of Allah? He said: 'He used to fast one day, and not the next, and he never fled if he met(the enemy in battle)."' He said: "How can I compare to him, O Prophet of Allah?" (Using translation from Nasāʾī 2401)   

بَلَغَ النَّبِيَّ ﷺ أَنِّي أَصُومُ أَسْرُدُ وَأُصَلِّي اللَّيْلَ قَالَ فَأَرْسَلَ إِلَيْهِ وَإِمَّا لَقِيَهُ قَالَ «أَلَمْ أُخْبَرْ أَنَّكَ تَصُومُ لَا تُفْطِرُ وَتُصَلِّي اللَّيْلَ؟ فَلَا تَفْعَلْ فَإِنَّ لِعَيْنَيْكَ حَظًّا وَلِنَفْسِكَ حَظًّا وَلِأَهْلِكَ حَقًّا صُمْ وَأَفْطِرْ وَصَلِّ وَنَمْ صُمْ مِنْ كُلِّ عَشَرَةِ أَيَّامٍ يَوْمًا وَلَكَ أَجْرُ تِسْعَةٍ» قَالَ إِنِّي أَقْوَى لِذَلِكَ يَا رَسُولَ اللهِ قَالَ «صُمْ صِيَامَ دَاوُدَ إِذًا» قَالَ وَكَيْفَ صِيَامُ دَاوُدَ يَا نَبِيَّ اللهِ؟ قَالَ «كَانَ يَصُومُ يَوْمًا وَيُفْطِرُ يَوْمًا وَلَا يَفِرُّ إِذَا لَاقَى» قَالَ وَمَنْ لِي بِهَذَا يَا نَبِيَّ اللهِ؟