It was narrated that Abu Salamah bin ‘Abdur-Rahman said:
“I entered upon ‘Abdullah bin ‘Amr and said: uncle, tell me what the Messenger of Allah صلی اللہ علیہ وآلہ وسلم said to you. He said: son of my brother, I had resolved to strive very hard until I said: I will fast for the rest of my life and I will read the whole Qur’an every day and The Messenger of Allah صلی اللہ علیہ وآلہ وسلم beard about that, and came in to Ine in my house, and said: I have heard that you said, I will fast for a lifetime and will read the Qur’an. I said: I did say that, Messenger of Allah صلی اللہ علیہ وآلہ وسلم. He said: Do not do that. Fast three days of each month. I said: I am able to do more than that. He said: fast two days of each week, Monday and Thursday. I said: I am able to do more than that. He said: Observe the fast of Dawfld, peace be upon him, for it is the best kind of fasting before Allah; one day fasting, and one day not fasting. And when he made a
promise he did not break it, and when he met (the enemy in battle) he did not flee.” (Sahih)