Sayyiduna Abdullah bin Amr bin al-As (may Allah be pleased with them both) said that the Messenger of Allah (peace and blessings be upon him) said to me: "You fast continually and stand in prayer every night." I said: Yes. He (peace and blessings be upon him) said: "When you do that, your eyes will become sunken and your soul will become exhausted. Whoever fasts all year round, none of his fasting will be accepted. Fast three days every month; that is the fasting of the whole year." He said: I said: I have the strength for more than that. He (peace and blessings be upon him) said: "Then fast like Dawud (peace be upon him): he would fast one day and not fast the next, and when he met the enemy he would not flee."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8473
Sayyiduna Abdullah bin Amr bin al-As (may Allah be pleased with them both) narrates that the Messenger of Allah (peace and blessings be upon him) said to me: "Have I not been informed that you are one who fasts by day and one who stands in prayer by night?" He said: I said: Yes, O Messenger of Allah (peace and blessings be upon him)! It is so. So he (peace and blessings be upon him) said: "Do not do so; rather, sleep and stand in prayer, fast and break your fast. Your body has a right over you, your eyes have a right over you, your wife has a right over you, and your guest has a right over you. It is sufficient for you to fast three days every month, for every good deed is (rewarded) tenfold; when you do this, you will be one who fasts perpetually." He said: I was strict, so strictness was imposed on me as well. I said: O Messenger of Allah (peace and blessings be upon him)! I have the strength. He (peace and blessings be upon him) said: "Then fast three days every week." He said: I was strict, so strictness was imposed on me. I said: O Messenger of Allah (peace and blessings be upon him)! I am able. He (peace and blessings be upon him) said: "Then keep the fasts of the Prophet of Allah, Dawud (peace be upon him), and do not exceed that." He said: I said: What were the fasts of the Prophet of Allah, Dawud (peace be upon him)? He (peace and blessings be upon him) said: "Half of the year."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8474
Ibn al-Mubarak (may Allah have mercy on him) said that al-Awza'i (may Allah have mercy on him) narrated the same hadith, except that he said: "Do not exceed it," and he added at the end that Abdullah bin Amr (may Allah be pleased with them both) used to say after he had grown old: "Would that I had accepted the concession of the Messenger of Allah (peace and blessings be upon him)."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8475
Sayyiduna Abu Qatadah (may Allah be pleased with him) narrates that a Bedouin came to him (peace and blessings be upon him) and said: "O Prophet of Allah! How is your fasting, or how do you (peace and blessings be upon him) fast?" The narrator said: He (peace and blessings be upon him) remained silent and did not give him any answer. When his (peace and blessings be upon him) anger had subsided, Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) asked: O Prophet of Allah (peace and blessings be upon him)! How do you (peace and blessings be upon him) fast, and tell us about the one who fasts the whole year? He (peace and blessings be upon him) said: "He has neither fasted nor broken his fast." Then he said: O Messenger of Allah! Tell us about the one who fasts two days and breaks his fast one day. He (peace and blessings be upon him) said: "O Umar! Who has the strength for that? I would love to do that." He said: O Messenger of Allah (peace and blessings be upon him)! What of the one who fasts one day and breaks his fast one day? He (peace and blessings be upon him) said: "That is the fasting of Dawud (peace be upon him)." Then he said: O Messenger of Allah! Tell us about the one who fasts the Day of Arafah. He (peace and blessings be upon him) said: "It wipes out the sins of one year and of the year before it." Then he said: O Messenger of Allah! Tell us about the one who fasts three days every month. He (peace and blessings be upon him) said: "That is the fasting of the whole year." Then he said: Tell us about the one who fasts the day of Ashura. He (peace and blessings be upon him) said: "The sins of one year will be forgiven." Then he said: O Messenger of Allah! Tell us about the one who fasts on Monday. He (peace and blessings be upon him) said: "That is the day on which I was born and on which prophethood was sent down upon me."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8476