Sahih Bukhari

Narrated `Abdullah bin `Amr:Allah's Messenger (ﷺ) was informed that I have said: ""By Allah, I will fast all the days and pray all the nights as long as I live."" On that, Allah's Messenger (ﷺ) asked me, ""Are you the one who says: 'I will fast all the days and pray all the nights as long as I live?' "" I said, ""Yes, I have said it."" He said, ""You cannot do that. So fast (sometimes) and do not fast (sometimes). Pray and sleep. Fast for three days a month, for the reward of a good deed is multiplied by ten times, and so the fasting of three days a month equals the fasting of a year."" I said, ""O Allah's Messenger (ﷺ)! I can do (fast) more than this."" He said, ""Fast on every third day. I said: I can do (fast) more than that, He said: ""Fast on alternate days and this was the fasting of David which is the most moderate sort of fasting."" I said, ""O Allah's Messenger (ﷺ)! I can do (fast) more than that."" He said, ""There is nothing better than that