Sahih al-Bukhari, Volume 3, Book 31, Hadith 196 (USC-MSA) ⓘ

Narrated `Abdullah bin `Amr bin Al-`As: Allah's Messenger said to me, "O `Abdullah! Have I not been informed that you fast during the day and offer prayers all the night." `Abdullah replied, "Yes, O Allah's Messenger!" The Prophet said, "Don't do that; fast for few days and then give it up for few days, offer prayers and also sleep at night, as your body has a right on you, and your wife has a right on you, and your guest has a right on you. And it is sufficient for you to fast three days in a month, as the reward of a good deed is multiplied ten times, so it will be like fasting throughout the year." I insisted (on fasting) and so I was given a hard instruction. I said, "O Allah's Messenger! I have power." The Prophet said, "Fast like the fasting of the Prophet David and do not fast more than that." I said, "How was the fasting of the Prophet of Allah, David?" He said, "Half of the year," (i.e. he used to fast on every alternate day). Afterwards when `Abdullah became old, he used to say, "It would have been better for me if I had accepted the permission of the Prophet (which he gave me i.e. to fast only three days a month).

حَدَّثَنَا ابْنُ مُقَاتِلٍ، أَخْبَرَنَا عَبْدُ اللَّهِ، أَخْبَرَنَا الأَوْزَاعِيُّ، قَالَ حَدَّثَنِي يَحْيَى بْنُ أَبِي كَثِيرٍ، قَالَ حَدَّثَنِي أَبُو سَلَمَةَ بْنُ عَبْدِ الرَّحْمَنِ، قَالَ حَدَّثَنِي عَبْدُ اللَّهِ بْنُ عَمْرِو بْنِ الْعَاصِ ـ رضى الله عنهما ـ قَالَ لِي رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ يَا عَبْدَ اللَّهِ أَلَمْ أُخْبَرْ أَنَّكَ تَصُومُ النَّهَارَ وَتَقُومُ اللَّيْلَ ‏"‏‏.‏ فَقُلْتُ بَلَى يَا رَسُولَ اللَّهِ‏.‏ قَالَ ‏"‏ فَلاَ تَفْعَلْ، صُمْ وَأَفْطِرْ، وَقُمْ وَنَمْ، فَإِنَّ لِجَسَدِكَ عَلَيْكَ حَقًّا، وَإِنَّ لِعَيْنِكَ عَلَيْكَ حَقًّا، وَإِنَّ لِزَوْجِكَ عَلَيْكَ حَقًّا، وَإِنَّ لِزَوْرِكَ عَلَيْكَ حَقًّا، وَإِنَّ بِحَسْبِكَ أَنْ تَصُومَ كُلَّ شَهْرٍ ثَلاَثَةَ أَيَّامٍ، فَإِنَّ لَكَ بِكُلِّ حَسَنَةٍ عَشْرَ أَمْثَالِهَا، فَإِنَّ ذَلِكَ صِيَامُ الدَّهْرِ كُلِّهِ ‏"‏‏.‏ فَشَدَّدْتُ، فَشُدِّدَ عَلَىَّ، قُلْتُ يَا رَسُولَ اللَّهِ، إِنِّي أَجِدُ قُوَّةً‏.‏ قَالَ ‏"‏ فَصُمْ صِيَامَ نَبِيِّ اللَّهِ دَاوُدَ عَلَيْهِ السَّلاَمُ وَلاَ تَزِدْ عَلَيْهِ ‏"‏‏.‏ قُلْتُ وَمَا كَانَ صِيَامُ نَبِيِّ اللَّهِ دَاوُدَ ـ عَلَيْهِ السَّلاَمُ ـ قَالَ ‏"‏ نِصْفَ الدَّهْرِ ‏"‏‏.‏ فَكَانَ عَبْدُ اللَّهِ يَقُولُ بَعْدَ مَا كَبِرَ يَا لَيْتَنِي قَبِلْتُ رُخْصَةَ النَّبِيِّ صلى الله عليه وسلم‏.‏