Chapter: Prohibition of Fasting for a lifetime for the one who will be harmed by that or who will neglect other duties, or does not break his fast on the two 'Ids or during the days of At-Tashriq; It is better to fast alternate days
Authentic
hadith of Sahih Muslim
Sahih Muslim 1159n
'Abdullah b. Amr (Allah be pleased with them) reported that the Messenger of Allah (ﷺ) had said to him:
Observe fast for a day and there would be reward for you for the rest (of the days). He said: I am capable of doing more than this. He then said: Observe fast for two days, and there would be reward for you for the rest (of the days). He said: I am capable of doing more than this. He (the Holy Prophet) said: Observe fast for three days and there would be reward for you for the rest of the days. He said: I am capable of doing more than this, whereupon he said: Observe fast for four days and there would be reward for you for the rest of the days. He said: I am capable of doing more than this. Thereupon he said: Then observe fast (which is the) best in the eye of Allah, the fast of David (peace be upon him) ; he used to observe fast one day and break on the other day.
Reported by Muslim (No. 1159n), An-Nasa’i (No. 2388, 2394) and Ahmad (No. 6621, 6802).
‘Abdullāh ibn ‘Amr ibn al-‘Ās (may Allah be pleased with him) reported: The Messenger of Allah (may Allah's peace and blessings be upon him) was told that I had said: "By Allah, I will fast every day and pray every night for as long as I live." The Messenger (may Allah's peace and blessings be upon…
"You fast continuously and stand in prayer at night?" I said: Yes. He said: "If you do that, your eyes will become weak, and your soul will become weary. No fasting counts for the one who fasts continuously. Fasting three days is like fasting the entire year". I said: Indeed, I am capable of more…