The Messenger of Allah ﷺ said to me, "I have been told that you stand in prayer all night and fast all day."I said, "Yes, Messenger of Allah."He said, "Then fast and break your fast, pray and sleep. Your body has a right over you, your wife has a right over you, and your guest has a right over you. It is enough for you to fast three days each month."I pressed for more, so he was strict with me. I said, "Messenger of Allah, I find I have the strength."He said, "Then fast three days each week."I pressed for more, so he was strict with me. I said, "Messenger of Allah, I find I have the strength."He said, "Then fast as the Prophet of Allah Dawud fasted, and do not exceed it."I said, "Messenger of Allah, what was the fast of Dawud?"He answered, "He would fast one day and break his fast the next."
حدثنا محمد بن مصعب حدثنا الأوزاعي عن يحيى عن أبي سلمة بن عبد الرحمن
قال لي رسول الله ﷺ لقد أخبرت أنك تقوم الليل وتصوم النهار قال قلت يا رسول الله نعم قال فصم وأفطر وصل ونم فإن لجسدك عليك حقا وإن لزوجك عليك حقا وإن لزورك عليك حقا وإن بحسبك أن تصوم من كل شهر ثلاثة أيام قال فشددت فشدد علي قال فقلت يا رسول الله إني أجد قوة قال فصم من كل جمعة ثلاثة أيام قال فشددت فشدد علي قال فقلت يا رسول الله إني أجد قوة قال صم صوم نبي الله داود ولا تزد عليه قلت يا رسول الله وما كان صيام داود قال كان يصوم يوما ويفطر يوما
Its isnad is sahih. Yahya is Ibn Abu Kathir. This hadith is a repetition of 6862 with similar wording. Bayhaqi reported it in 4:299-300 through the route of Walid bin Mazid and through the route of Abdullah bin Mubarak, both of them from Uzai, then he said, Bukhari reported it from Muhammad bin Muqatil from Ibn Mubarak, and Muslim reported it from the hadith of Ikrima bin Ammar and Husayn Muallim from Yahya bin Abu Kathir. The narration of Bukhari to which he referred is in Fath al-Bari 4:189-190, and he also reported it with the same isnad in abbreviated form at 9:262. Muslim's narration of it is at 1:319.