It was narrated that Abu Qatadah said: “Umar said: ‘Messenger of Allah, what about a person who fasted for an entire lifetime?’ He said: ‘He neither fasted nor broke his fast.’ He said: ‘Messenger of Allah ﷺ, what about a person who fasted for two days, and broke his fast for one day?’ He said: ‘Can anyone do that?’ He said: ‘What about a person who fasted for one day, and broke his fast for one day?’ He said: ‘That is the fast of Dawood علیہ السلام, peace be upon him.’ He said: ‘What about a person who fasted for one day, and broke his fast for two days?’ He said: ‘I wish that I could do that.’ Then he said: ‘Three days of each month, and from Ramadan to Ramadan, this is fasting for an entire lifetime.” (Sahih)