Fasting is a protection from lusts:
1- Al Bukhari reported from the Hadith of Abu Hurayrah (may Allah be pleased with him) that the Prophet (peace be upon him) said: "Fasting is a shield (or a screen or a shelter). So, the person observing fasting 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 tell him twice, 'I am fasting." The Prophet (peace be upon him) added: "By Him in Whose Hands my soul is, the smell coming out from the mouth of a fasting person is better in the sight of Allah than the smell of musk. (Allah says about the fasting person), 'He has left his food, drink and desires for My sake. The fast is for Me. So I will reward (the fasting person) for it and the reward of good deeds is multiplied ten times."
2- Imam Ahmad reported from the Hadith of Jabir (may Allah be pleased with him) that the Prophet (peace be upon him) said: "O Ka`b `Ujrah, fasting is a strong shield, sadaqah erases sins as water extinguishes fire, and prayer is evidence -or he said: something to draw you nearer to Allah. O Ka`b ibn `Ujrah, people are of two types: One who purchases himself [by doing righteous deeds] and by this he shall protect himself and a person who sells himself [for Hell]."
3- Imam Ahmad also reported from the Hadith of `Abdullah ibn `Amr that the Prophet (peace be upon him) said: "The castration [things which abate sexual desires] of my nation is fasting." Fasting abates sexual desires and narrows the ways of Satan. Therefore, the Prophet (peace be upon him) described fasting for youth who have no power to marriage to rectify their manners, abate their sexual desire, and promote their behavior.
4- Al Bukhari reported from the Hadith of `Abdullah ibn Mas`ud (may Allah be pleased with him) who said: The Messenger of Allah (peace be upon him)said to us: "O young people! He who can afford to marry should marry, because it will help him refrain from looking at other women, and save his private parts from looking at other women, and save his private parts from committing illegal sexual relation; and he who cannot afford to marry is advised to fast, as fasting will diminish his sexual power."
Sheikh `Umar Al Ashqar said:
Fasting is a protection for a person from sins and faults, foul language, and bad actions, thereby a person protects himself from Hell.
Al Munawy (may Allah bestow mercy on his soul) said in Faydul-Qadir: Fasting is a protection in the world from sins where it abates sexual desires because fullness brings about sexual desires and causes laziness, therefore the Prophet (peace be upon him) said: "No man fills a container worse than his stomach." When a person eats to his full, his insight becomes weak, his ideas becomes distorted, laziness and sleep overcome him and stop him from worship, and his anger and sexual desires become intense and he may fall into sins.
Some Pious Predecessors said: Glad tidings are for those who abandon a present lust for an unseen encounter.
O people who observe fast, let it be known that whoever abstains from the worldly desires shall gain reward in Paradise.
Allah (may He be Exalted) says: "Eat and drink at ease for that which you have sent on before you in days past!" [Surat Al Haqqah: 24].
Mujahid and others said: It was revealed concerning fasting people.
Let it be known that whoever abstains from the things which Allah forbade shall have a carnival day when he meets His Lord.
"Whoever hopes for the Meeting with Allah, then Allah's Term is surely coming." [Surat Al `Ankabut: 5].
Fasting is a penance for sins:
Allah (may He be Exalted) says: "The men and the women who observe Saum (fast) (the obligatory fasting during the month of Ramadân, and the optional Nawâfil fasting), the men and the women who guard their chastity (from illegal sexual acts) and the men and the women who remember Allâh much with their hearts and tongues - Allâh has prepared for them forgiveness and a great reward (i.e. Paradise)." [Surat Al Ahzab: 35].
1- Al Bukhari and Muslim reported from the Hadith of Hudhayfah (may Allah be pleased with him) that the Prophet (peace be upon him) said: "There would (first) be turmoil for a person in regard to his family, his property, his own self, his children, his neighbors(and the sins comnaitted in their connection) would be expiated by fasting,prayer, charity,enjoining good and prohibiting evil."
Al Munawy (may Allah bestow mercy on his soul) said: Turmoil for a person means error and sin or the evil he encounters.
• To his family means the greif and sad which he suffers with them or his business and neglecting their rights.
• His property means he takes money from proper or improper ways and spends it in unlawful ways of expenditure.
• His children means by loving him and engaging with him rather than focusing on legal duties.
• His neighbor means the envy, pride, and negligence they practice against a person.
Moreover, the Prophet (peace be upon him) focused on the real acts of worship such as Salah, Fasting, Zakah, and enjoing good and fobidding evil.
2- Al Bukhari and Muslim also reported: "Whoever fasts in the month of Ramadan out of sincere faith, and hoping for a reward from Allah, then all his previous sins will be forgiven."
3- Imam Muslim reported on the authority of Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (peace be upon him) said: "The five daily Salah, and from one Friday Salah to (the next) Friday Salah, and Ramadan to Ramadan are expiation of the sins committed in between them, so long as major sins are avoided."
So, how great is that month in which sins are forgiven, evil deeds are expiated, and a person obtains the satisfaction and forgiveness of the Lord of the heavens and the earth.
4- It was reported by At-Tabarany in Al Mu`jam Al Awsat on the authority of Abu Sa`id (may Allah be pleased with him) that the Prophet (peace be upon him) said: "Fasting on the Day of `Arafah expiates the past and the following sins of the year." 
5- Imam Muslim reported on the authority of Abu Qatadah (may Allah be pleased with him) that the Messenger of Allah (peace be upon him) said: "Fasting the Day of `Arafah (9th of Dhul-Hijjah) I hope from Allah that it atones the sins of the preceding and the coming year, and fasting the Day of `Ashura' (10th of Muharram), I hope from Allah that it expiates the sins of the past year."
• It atones the sins of the past year means: The committed sins.
• And following year means that Allah (may He be Exalted) protects him from committed sins or gives rewards to equal the sins committed in that year or even atone them for real.
Therefore, the author of Al `Uddah [Abu `Abdullah, Al Husayn ibn Ali At-Tabary] said: There is nothing equal to fasting among the acts of worship.
 Sahih Al Jami`: 3805.
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