It is narrated from Sayyiduna Abdullah bin Amr bin al-As (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) was informed that I had said: "As long as I live, I will stand (in prayer) all night and fast by day." So the Messenger of Allah (peace and blessings be upon him) said (to me): "Are you the one who said: By Allah, as long as I live I will fast by day and stand (in prayer) at night?" I said: O Messenger of Allah, I did say it. He (peace and blessings be upon him) said: "You will not be able to bear that. So pray and also sleep, fast and also break your fast, and fast three days of every month, for a good deed is rewarded tenfold, and that is equal to fasting all the time." I said: I am able to do something better than that. He (peace and blessings be upon him) said: "Then fast one day and break your fast for two days." I said: I am able to do something better than that. The Messenger of Allah (peace and blessings be upon him) said: "Fast one day and break your fast one day; that is the fast of Dawud (peace be upon him), and it is the most balanced fasting." I said: I am able to do something better than that. The Messenger of Allah (peace and blessings be upon him) said: "There is no fasting better than that."
Imam al-Tabarani (may Allah have mercy on him) said: "Only Ya'la bin al-Harith narrated this hadith from Bakr bin Wa'il, and only his son from Ya'la, and Ali bin Muslim al-Mu'addib is alone in narrating it."