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 time, 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."
Sahih al-Bukhari Book 60, Hadith 90
I, along with a group of people, gave the pledge of allegiance to Allah's Messenger (ﷺ). He said, "I take your
Pledge on the condition that you (1) will not join partners in worship with Allah, (2) will not steal, (3)
will not commit illegal sexual intercourse, (4) will not kill your offspring, (5) will not slander, (6) and
will not disobey me when I order you to do good. Whoever among you will abide by his pledge, his
reward will be with Allah, and whoever commits any of those sins and receives the punishment in this
world, that punishment will be an expiation for his sins and purification; but if Allah screens him, then
it will be up to Allah to punish him if He will or excuse Him, if He will."
Sahih al-Bukhari Book 97, Hadith 94