Sahih Al-Bukhari – Volume 3 – Book 30 – P.78
(1) CHAPTER. Fasting is obligatory in (the month of) Ramadan. And the Statement of Allah
“O, you who believe! Observing As-Saum (the fasting) is prescribed for you as it was prescribed for those before you, that you may become Al-Muttaqun” [Quran 2:183].
1891. Narrated Talba bin ‘Ubaid-UlIãh: A bedouin with unkempt hair came to Allah’s Messenger, peace be upon him, and said, “0 Allah’s Messenger! Inform me what Allah has made compulsory for me as regards As-Salat (the prayer) .” He replied: “You have to perform the five compulsory Salat (Iqamat-As-Salat) in a day and night (24 hours), unless you want to offer Nawafil .” The bedouin further asked, “Inform me what Allah has made compulsory for me as regards fasting.” He replied, “You have to observe Saum (fast) during the whole month of Ramadan, unless you want to fast more as Nawafil.” The bedouin further asked, “Tell me how much Zakãt Allah has enjoined on me.” Thus, Allah’s Messenger, peace be upon him, informed him about all the laws (i.e., fundamentals) of Islam. The bedouin then said, “By Him Who has honoured you, I will neither perform any Nawafil nor will I decrease what Allah has enjoined on me.” Allah’s Messenger, peace be upon him, said, “If he is saying the truth, he will succeed (or said, he will be granted Paradise) .”
Sahih Al-Bukhari – Volume 3 – Book 30 – P.79
1892. Narrated Ibn ‘Umar: The Prophet, peace be upon him, observed the Saum (fast) on the 10th of Muharram (‘Ashura’), and ordered (Muslims) to observe Saum (fast) on that day, but when the fasting of the month of Ramadan was prescribed, the fasting of the ‘Ashura’ was abandoned. ‘Abdullah did not use to observe fast on that day unless it coincided with his routine fasting by chance.
1893. Narrated ‘Aishah: (The tribe of) Quraish used to observe Saum (fast) on the day of ‘Ashura’ in the Pre-Islamic Period, and then Allah’s Messenger, peace be upon him, ordered (Muslims) to observe Saum (fast) on it till the fasting in the month of Ramadan was prescribed; whereupon the Prophet, peace be upon him, said, “He who wants to fast (on ‘Ashura’) may fast, and he who does not want to observe Saum (fast) may not fast.”
1894. Narrated Abu Hurairah: Allah’s Messenger, peace be upon him, said, “Saum (fasting) is a shield (or a screen or a shelter from the Hell-fire). So, the person observing Saum (fast) should avoid sexual relation with his wife and should not behave foolishly and impudently, and if somebody fights with him or abuses him, he should say to him twice, ‘I am observing Saum (fast).” The Prophet, peace be upon him, added, “By Him in Whose Hands my soul is, the smell coming out from the mouth of a person observing Saum (fast) is better with Allah than the smell of musk. (Allah says about the fasting person), ‘He has left his food, drink ad sexual desires for My sake. The Saum (fast) is for Me. So I will reward (the fasting person) for it and the reward of good deeds is multiplied ten times.’”
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(4) CHAPTER. Ar-Raiyãn (one of the gates of Paradise) is for people observing Saum (fast) people.
1896. Narrated SahI: The Prophet, peace be upon him, said, “There is a gate in Paradise called Ar-Raiyan, and those who observe Saum (fasts) will enter through it on the Day of Resurrection and none except them will enter through it. It will be said, ‘Where are those who used to observe Saum (fast)?’ They will get up, and none except them will enter through it. After their entry the gate will be closed and nobody will enter through it.”
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1897. Narrated Abu Hurairah: Allah’s Messenger, peace be upon him, said, “Whoever gives two kinds (of things or property) in charity for Allah’s Cause, will be called from the gates of Paradise and will be addressed, ‘O slaves of Allah! Here is prosperity.’ So, whoever was amongst the people who used to offer their Salat (prayers), will be called from the gate of the Salat; and whoever was amongst the people who used to participate in Jihad, will be called from the gate of Jihad; and whoever was amongst those who used to observe fasts, will be called from the gate of Ar-Raiyan; whoever was amongst those who used to give As-Sadaqa (charity), will be called from the gate of As-Sadaqa.” Abu Bakr said, “Let my parents be sacrificed for you, O Allah’s Messenger! No distress or need will befall him who will be called from those gates. Will there be any one who will be called from all these gates?” The Prophet, peace be upon him, replied, “Yes, and I hope you will be one of them.”
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(5) CHAPTER. Should it be said “Ramadãn” or “the month of Ramadan?” And whoever thinks that both are permissible.
And the Prophet, peace be upon him, said, “Whoever observe Saum (fasts) in Ramadan.” And also said, “Do not observe Saum before Ramadan.**”
1899. Narrated Abu Hurairah: Allah’s Messenger, peace be upon him, said, “When the month of Ramadan begins, the gates of Paradise are opened and the gates of Hell are closed and the devils are chained.”
1900. Narrated Ibn ‘Umar: I heard Allah’s Messenger, peace be upon him, saying, “When you see the crescent (of the month of Ramadan), start observing Saum (fast) and when you see the crescent (of the month of Shawwãl), stop observing Saum; and if the sky is overcast (and you can’t see it) then regard the crescent (month) of Ramadan (as of 30 days).”