Hadith: There is no fasting superior to the fast of my brother Dawūd; fasting half of one's life by fasting one day and eating one day

عن عبد الله بن عَمْرِو بن العاص رضي الله عنهما قال: «أُخبِر رسول الله صلى الله عليه وسلم أني أقول: والله لَأَصُومَنَّ النهار، وَلَأَقُومَنَّ الليل مَا عِشْتُ. فقال رسول الله صلى الله عليه وسلم : أنت الذي قلتَ ذلك؟ فقلتُ له: قد قُلتُه -بأبي أنت وأمي-. فقال: فإنك لا تستطيع ذلك، فصُم وأفطِر، وَقُمْ وَنَمْ ، الشَّهْرِ ثَلاَثَةَ أَيَّامٍ، فَإِنَّ الحَسَنَةَ بِعَشْرِ أَمْثَالِهَا، وذلك مثل صيام الدَّهْرِ. قلت: فإني أُطِيقُ أفضل من ذلك. قال: فصم يوما وأَفطر يومين. قلت: أُطِيقُ أفضل من ذلك. قال: فصم يوما وأفطر يوما، فذلك مثل صيام داود، وهو أفضل الصيام. فقلت: إني أُطِيقُ أفضل من ذلك. قال: لا أفضل من ذلك»، وفي رواية: «لا صوم فوق صوم أخي داود -شَطْرَ الدَّهَرِ-، صم يوما وأفطر يوما».
[صحيح] - [متفق عليه]

‘Abdullāh ibn ‘Amr ibn al-‘Ās (may Allah be pleased with him) reported: The Messenger of Allah (may Allah's peace and blessings be upon him) was told that I had said: "By Allah, I will fast every day and pray every night for as long as I live." The Messenger (may Allah's peace and blessings be upon him) asked me: "Are you the one who said that?" I said: "Yes, I said it; by my father, you and my mother." He said: "You would not be able to do that. So fast and break your fast, pray and sleep. Fast for three days a month. The reward of a good deed is multiplied by ten, so the fasting of three days a month equals the fasting of a year." I said: "I can do (fast) more than this." He said: "Fast one day every three days." I said: "I can do more than that." He said: "Fast every other day; this was the fasting of Dawūd and the best form of fasting." I said: "I can do better than that." He said: "There is nothing better than that." In another narration, the Prophet (may Allah's peace and blessings be upon him) said: "There is no fasting superior to the fast of my brother Dawūd; fasting half of one's life by fasting one day and eating one day."
Sahih/Authentic. - [Al-Bukhari and Muslim]

Explanation

The Prophet (may Allah's peace and blessings be upon him) was told that ‘Abdullāh ibn ‘Amr swore to fast every day and stay in prayer all night without sleep for his entire life. So he asked him whether he had said that and he answered that he had. The Prophet told him that such a commitment would be beyond his endurance, so he should combine worship with rest by fasting and eating; praying at night and sleeping and restricting his voluntary fasting to three days a month, which would grant him the reward of fasting the whole year. However, ‘Abdullāh said that he could handle more than that. He kept asking to do more fasting until he reached its ultimate form, which is fasting like Prophet Dawūd, namely fasting every other day. He asked to do more from a desire to do more good deeds, but the Prophet (may Allah's peace and blessings be upon him) told him that there was no fast better than that.