"The Messenger of Allah said to me: 'Fast one day of the month and you will have the reward of what is left.' I said: 'I am able to do more than that.' He said: 'Fast two days and you will have the reward of what is left.' I said: 'I am able to do more than that.' He said: 'Fast three days and you will have the reward of what is left.' I said: 'I am able to do more than that.' He said: 'Fast four days and you will have the reward of what is left.' I said: ' I am able to do more than that.' The messenger of Allah said: 'The best fasting is the fast of Dawud; he used to fast one day and not the next."' 2406. It was narrated that Abu Dharr said: "My beloved Prophet advised me to do three things which I will never give up, if Allah wills. He advised me to pray Duha to pray Witr before sleeping, and to fast three days of each month."
Mu‘ādhah al-‘Adawiyah reported that she asked ‘Ā’ishah (may Allah be pleased with her): “Did the Messenger of Allah (may Allah's peace and blessings be upon him) fast three days of each month?” ‘Ā’ishah replied: 'Yes.' Mu‘ādhah asked: “In which part of the month did he fast?” ‘Ā’ishah replied: “It…