Hadith
أَخْبَرَنَا مُحَمَّدُ بْنُ عُبَيْدٍ، عَنْ أَسْبَاطٍ، عَنْ مُطَرِّفٍ، عَنْ حَبِيبِ بْنِ أَبِي ثَابِتٍ، عَنْ أَبِي الْعَبَّاسِ، عَنْ عَبْدِ اللَّهِ بْنِ عَمْرٍو، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " إِنَّهُ بَلَغَنِي أَنَّكَ تَقُومُ اللَّيْلَ وَتَصُومُ النَّهَارَ " . قُلْتُ يَا رَسُولَ اللَّهِ مَا أَرَدْتُ بِذَلِكَ إِلاَّ الْخَيْرَ . قَالَ " لاَ صَامَ مَنْ صَامَ الأَبَدَ وَلَكِنْ أَدُلُّكَ عَلَى صَوْمِ الدَّهْرِ ثَلاَثَةُ أَيَّامٍ مِنَ الشَّهْرِ " . قُلْتُ يَا رَسُولَ اللَّهِ إِنِّي أُطِيقُ أَكْثَرَ مِنْ ذَلِكَ . قَالَ " صُمْ خَمْسَةَ أَيَّامٍ " . قُلْتُ إِنِّي أُطِيقُ أَكْثَرَ مِنْ ذَلِكَ . قَالَ " فَصُمْ عَشْرًا " . فَقُلْتُ إِنِّي أُطِيقُ أَكْثَرَ مِنْ ذَلِكَ . قَالَ " صُمْ صَوْمَ دَاوُدَ عَلَيْهِ السَّلاَمُ كَانَ يَصُومُ يَوْمًا وَيُفْطِرُ يَوْمًا " .
It was narrated that 'Abdullah bin 'Amr said:"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
Sahih · Abu Ghuddah
Sunan an-Nasa'i 2397 ·Book 22, Hadith 308·Also available on sunnah.com·