Sunan an-Nasa'i, Volume 3, Book 22, Hadith 2393 (DarusSalam) ⓘ

It was narrated that 'Abdullah said: "The Messenger of Allah entered my apartment and said: "I have been told that you stand all night (in prayer) and fast all day.' I said: 'Yes (I do).' He said: 'Do not do that. Sleep and stand (in prayer); fast and break your fast. For your eyes have a right over you, your body has a right over you, your body has a right over you, your wife has a right over you, your guest has a right over you, and your friend has a right over you. I hope that you will have a long life and that it will be sufficient for you to fast three days of each month. That is fasting for a lifetime, because a good deed is equal to ten like it.' I said : 'I feel able to do more.' I was strict, so I was dealt with strictly. He said: 'Fast three days each week.' I said: 'I am ableto do more thtn that; I was strict, so I was dealt with strictly. He said: 'Observe the fast of the Prophet of Allah, Dawud, peace be upon him. I said: 'What was the fast of Dawud?' he said: 'Half of a lifetime."' '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."

أَخْبَرَنَا يَحْيَى بْنُ دُرُسْتَ، قَالَ حَدَّثَنَا أَبُو إِسْمَاعِيلَ، قَالَ حَدَّثَنَا يَحْيَى بْنُ أَبِي كَثِيرٍ، أَنَّ أَبَا سَلَمَةَ، حَدَّثَهُ أَنَّ عَبْدَ اللَّهِ قَالَ دَخَلَ رَسُولُ اللَّهِ صلى الله عليه وسلم حُجْرَتِي فَقَالَ ‏"‏ أَلَمْ أُخْبَرْ أَنَّكَ تَقُومُ اللَّيْلَ وَتَصُومُ النَّهَارَ ‏"‏ ‏.‏ قَالَ بَلَى ‏.‏ قَالَ ‏"‏ فَلاَ تَفْعَلَنَّ نَمْ وَقُمْ وَصُمْ وَأَفْطِرْ فَإِنَّ لِعَيْنِكَ عَلَيْكَ حَقًّا وَإِنَّ لِجَسَدِكَ عَلَيْكَ حَقًّا وَإِنَّ لِزَوْجَتِكَ عَلَيْكَ حَقًّا وَإِنَّ لِضَيْفِكَ عَلَيْكَ حَقًّا وَإِنَّ لِصَدِيقِكَ عَلَيْكَ حَقًّا وَإِنَّهُ عَسَى أَنْ يَطُولَ بِكَ عُمُرٌ وَإِنَّهُ حَسْبُكَ أَنْ تَصُومَ مِنْ كُلِّ شَهْرٍ ثَلاَثًا فَذَلِكَ صِيَامُ الدَّهْرِ كُلِّهِ وَالْحَسَنَةُ بِعَشْرِ أَمْثَالِهَا ‏"‏ ‏.‏ قُلْتُ إِنِّي أَجِدُ قُوَّةً فَشَدَّدْتُ فَشُدِّدَ عَلَىَّ ‏.‏ قَالَ ‏"‏ صُمْ مِنْ كُلِّ جُمُعَةٍ ثَلاَثَةَ أَيَّامٍ ‏"‏ ‏.‏ قُلْتُ إِنِّي أُطِيقُ أَكْثَرَ مِنْ ذَلِكَ فَشَدَّدْتُ فَشُدِّدَ عَلَىَّ ‏.‏ قَالَ ‏"‏ صُمْ صَوْمَ نَبِيِّ اللَّهِ دَاوُدَ عَلَيْهِ السَّلاَمُ ‏"‏ ‏.‏ قُلْتُ وَمَا كَانَ صَوْمُ دَاوُدَ قَالَ ‏"‏ نِصْفُ الدَّهْرِ ‏"‏ ‏.‏