“I [Usamah bin Zaid (ra)] said, ‘O Messenger of Allah [saws] sometimes you fast and you hardly ever break your fast and sometimes you do not fast and you hardly ever fast and sometimes you do not fast and you hardly ever fast except for two days which if you are fasting you include them in your fast and if you are not fasting then you fast them on your own.’ He said, ‘Which two days?’ I said, ‘Monday and Thursday.’ He said, ‘Those are two days in which deeds are shown to the Lord of the worlds, and I like my deeds to be shown when I am fasting.’”[65]
“O Messenger of Allah [saws] why do you fast on Mondays and Thursdays?” He said, “On Mondays and Thursdays Allah [swt] forgives every Muslim except two who have forsaken one another. He says, ‘Leave these two until they reconcile.’”[66]
Fasting three days of every month
“The Messenger of Allah [saws] commanded me [Abu Hurairah (ra)] to pray two raka’ah of duha and not to sleep until I had prayed Witr and to fast three days each month.”[67]
“The Messenger of Allah [saws] enjoined three things upon me [Abu Hurairah (ra)]: to sleep after praying Witr, to perform ghusl on Friday and to fast three days of each month.”[68]
“I [Mu’Adhah Al-‘Adawiyyah (ra)] said to ‘A’ishah [ra], ‘Did the Messenger of Allah [saws] fast three days every month?’ She said, ‘Yes.’ I said, ‘Which days of the month would he fast?’ She said, ‘He was not specific about any particular day of the month he fasted.’”[69]
“A man came to the Messenger of Allah [saws] and said, ‘O Messenger of Allah [saws] what do you say about a man who fasted for the rest of his life?’ The Messenger of Allah [saws] said, ‘I wish that he would never eat for the rest of his life.’ He said, ‘Two-thirds [of a lifetime]?’ He said, ‘That is too much.’ He said, ‘Half?’ He said, ‘That is too much.’ He said, ‘Shall I not tell you of that which will take away impurity from the heart?’ He said, ‘Yes.’ He said, ‘Fasting for three days each month.’”[70]
“I [Abu Hurairah (ra)] heard the Messenger of Allah [saws] say, ‘The month of patience [Ramadan] and three days of each month is fasting for a lifetime.”[71]
“I [‘Uthman bin Abi Al-‘As (ra)] heard the Messenger of Allah [saws] say, ‘It is a good fast to fast three days of each month.’”[72]
“I [Al-Hurr bin Sayyah (ra)] heard Ibn ‘Umar [ra] say, ‘The Prophet [saws] used to fast three days of each month.’”[73]