Sunan an-Nasa’i 2394
The Book of Fasting
Mention of fasting more or less, and mentioning the differences reported in the narration Of 'Abdullah Bin 'Amr About That
It was narrated from 'Abdullah bin 'Amr that the Messenger of Allah (ﷺ) said to him: "Fast one day, and you will have the reward of what is left." He said: "I am able to do more than that." He (ﷺ) said: "Fast two days, and you will have the reward of what is left." He said: "I am able to do more than that." He (ﷺ) said: "Fast three days and you will have the reward of what is left." He said: "I am able to do more than that." He (ﷺ) said: "Fast four days and you will have the reward of what is left." He said: "I am able to do more than that." He (ﷺ) said: "Observe the best kind of fasting before Allah, the fast of Dawud, peace be upon him; he used to fast one day and break his fast for one day." 'Ata said: "Someone who heard him told me that Ibn 'Umar (said) that the Prophet (ﷺ) said: 'Whoever fasts every day of his life, then he has not fasted.'"