Sahih Bukhari Volume 4, Book 60, Hadith 3419

حَدَّثَنَا يَحْيَى بْنُ بُكَيْرٍ، حَدَّثَنَا اللَّيْثُ، عَنْ عُقَيْلٍ، عَنِ ابْنِ شِهَابٍ، أَنَّ سَعِيدَ بْنَ الْمُسَيَّبِ، أَخْبَرَهُ وَأَبَا، سَلَمَةَ بْنَ عَبْدِ الرَّحْمَنِ أَنَّ عَبْدَ اللَّهِ بْنَ عَمْرٍو ـ رضى الله عنهما ـ قَالَ أُخْبِرَ رَسُولُ اللَّهِ صلى الله عليه وسلم أَنِّي أَقُولُ وَاللَّهِ لأَصُومَنَّ النَّهَارَ وَلأَقُومَنَّ اللَّيْلَ مَا عِشْتُ‏.‏ فَقَالَ لَهُ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ أَنْتَ الَّذِي تَقُولُ وَاللَّهِ لأَصُومَنَّ النَّهَارَ وَلأَقُومَنَّ اللَّيْلَ مَا عِشْتُ ‏"‏ قُلْتُ قَدْ قُلْتُهُ‏.‏ قَالَ ‏"‏ إِنَّكَ لاَ تَسْتَطِيعُ ذَلِكَ، فَصُمْ وَأَفْطِرْ، وَقُمْ وَنَمْ، وَصُمْ مِنَ الشَّهْرِ ثَلاَثَةَ أَيَّامٍ، فَإِنَّ الْحَسَنَةَ بِعَشْرِ أَمْثَالِهَا، وَذَلِكَ مِثْلُ صِيَامِ الدَّهْرِ ‏"‏‏.‏ فَقُلْتُ إِنِّي أُطِيقُ أَفْضَلَ مِنْ ذَلِكَ يَا رَسُولَ اللَّهِ‏.‏ قَالَ ‏"‏ فَصُمْ يَوْمًا وَأَفْطِرْ يَوْمَيْنِ ‏"‏‏.‏ قَالَ قُلْتُ إِنِّي أُطِيقُ أَفْضَلَ مِنْ ذَلِكَ‏.‏ قَالَ ‏"‏ فَصُمْ يَوْمًا وَأَفْطِرْ يَوْمًا، وَذَلِكَ صِيَامُ دَاوُدَ، وَهْوَ عَدْلُ الصِّيَامِ ‏"‏‏.‏ قُلْتُ إِنِّي أُطِيقُ أَفْضَلَ مِنْهُ يَا رَسُولَ اللَّهِ‏.‏ قَالَ ‏"‏ لاَ أَفْضَلَ مِنْ ذَلِكَ ‏"‏‏.‏

Narrated By Abdullah bin Amr : Allah's Apostle was informed that I have said: "By Allah, I will fast all the days and pray all the nights as long as I live." On that, Allah's Apostle asked me. "Are you the one who says: 'I will fast all the days and pray all the nights as long as I live?' " I said, "Yes, I have said it." He said, "You cannot do that. So fast (sometimes) and do not fast (sometimes). Pray and sleep. Fast for three days a month, for the reward of a good deed is multiplied by ten time, and so the fasting of three days a month equals the fasting of a year." I said, "O Allah's Apostle! I can do (fast) more than this." He said, "Fast on every third day. I said: I can do (fast) more than that, He said: "Fast on alternate days and this was the fasting of David which is the most moderate sort of fasting." I said, "O Allah's Apostle! I can do (fast) more than that." He said, "There is nothing better than that."