Sayyiduna Abu Qatadah (may Allah be pleased with him) narrates: A Bedouin asked the Prophet Muhammad (peace and blessings be upon him) about always fasting (i.e., keeping a voluntary fast every day). The Prophet (peace and blessings be upon him) said: Such a person has neither fasted nor left fasting (the narrator is in doubt, perhaps these are the words), neither has he left fasting nor has he fasted. Then another person stood up and said: O Messenger of Allah! What is your opinion about a person who fasts three days every month? The Prophet (peace and blessings be upon him) said: This is equivalent to always (i.e., the whole month) keeping voluntary fasts. That person said: What is your opinion about a person who fasts on Mondays? The Prophet (peace and blessings be upon him) said: This is the day on which I was born and on which (the Qur’an or revelation) was sent down to me. That person said: What is your opinion about a person who fasts one day and does not fast the next day? The Prophet (peace and blessings be upon him) said: This is the way my brother, Sayyiduna Dawud (David), peace be upon him, used to fast.