The Prophet (saws) said: Do not fast one day or two days just before Ramadan except in the case of a man who has been in the habit or observing a fast (on that day); and do not fast until you sight it (the moon). Then fast until you sight it. If a cloud appears on that day (i.e. 29th of Ramadan) then complete the number thirty (days) and then end the fasting: a month consists of twenty-nine days.

Allah's Apostle entered upon me and said, "Have I not been informed that you offer prayer all the night and fast the whole day?" I said, "Yes." He said, "Do not do so; Offer prayer at night and also sleep; Fast for a few days and give up fasting for a few days because your body has a right on you, and your eye has a right on you, and your guest has a right on you, and your wife has a right on you. I hope that you will have a long life, and it is sufficient for you to fast for three days a month as the reward of a good deed, is multiplied ten times, that means, as if you fasted the whole year." I insisted (on fasting more) so I was given a hard instruction. I said, "I can do more than that (fasting)" The Prophet said, "Fast three days every week." But as I insisted (on fasting more) so I was burdened. I said, "I can fast more than that." The Prophet said, "Fast as Allah's prophet David used to fast." I said, "How was the fasting of the prophet David?" The Prophet said, "One half of a year (i.e. he used to fast on alternate days). '

A bedouin with unkempt hair came to Allah's Apostle and said, "O Allah's Apostle! Tell me what Allah has enjoined on me as regards prayers." The Prophet said, "You have to offer perfectly the five (compulsory) prayers in a day and a night (24 hrs.), except if you want to perform some extra optional prayers." The bedouin said, "Tell me what Allah has enjoined on me as regards fasting." The Prophet said, "You have to observe fast during the month of Ramadan except if you fast some extra optional fast." The bedouin said, "Tell me what Allah has enjoined on me as regard Zakat." The Prophet then told him the Islamic laws and regulations whereupon the bedouin said, "By Him Who has honored you, I will not perform any optional deeds of worship and I will not leave anything of what Allah has enjoined on me." Allah's Apostle said, "He will be successful if he has told the truth (or he will enter Paradise if he said the truth)." And some people said, "The Zakat for one-hundred and twenty camels is two Hiqqas, and if the Zakat payer slaughters the camels intentionally or gives them as a present or plays some other trick in order to avoid the Zakat, then there is no harm (in it) for him.