‘Abdullaah bin Saalih Al-Fawzaan
Ahaadeeth As-Siyaam: Ahkaam wa Adaab (pg. 27-29)
Abu Hurairah (radyAllaahu ‘anhu) reported that the Messenger of Allaah (sallAllaahu ‘alayhi wa sallam) said: “Every deed of the Son of Aadam will be rewarded ten to seven hundred times its worth. Allaah, Mighty and Sublime, said: ‘Except for the fast, for indeed it is for Me, and I will reward it. He leaves off his desires and his food for My sake. There are two times of joy for the one fasting. The time of joy when he breaks his fast and the time of joy when he meets His lord. And the scent coming from the mouth of the one fasting is more pleasant in the sight of Allaah than the smell of musk.'” 
This hadeeth is proof for the virtue of fasting and the great station it possesses in the sight of Allaah. Four of its many virtues occur in this hadeeth, and they are:
1. Those who fast will receive their reward in full without any reckoning, for every good deed is rewarded ten to seven hundred times its like in worth, except for the fast. Indeed, its reward is not limited to this number, but rather Allaah will reward it with manifold its likes in worth. This is because the fast is from (the forms of) patience and Allaah has stated:
“Verily, the patient ones will be given their reward in full without any reckoning.” 
Al-Awzaa’ee said of this (ayah): “It will neither be weighed for them nor measured, but rather it will simply be served to them as food is served.” 
2. Indeed Allaah connected the fast to Himself in conjunctive form, above all other types of deeds. And this conjunction is enough to show its noble status. This, and Allaah knows best, is due its state of encompassing the entirety of the day. Thus, one can find that the individual fasting has neglected his desires, while his soul constantly yearns after them. This, along with its lengthened duration, is not found in anything else besides the fast, especially in the days of summer due to their length and severity in heat. The individual’s abandonment of the things he desires is an act of worship, which will be rewarded. This is because the fast is a secret kept between the servant and his Lord. No one knows of it except Allaah, the most High. It is an inward (hidden) action, which cannot be seen by the creation, thus riyaa’ (showing off) cannot enter into it.
3. When the one who fasts meets his Lord, he will be delighted by his fast due to what he will see in it from its abundance, good standing and his reward by having his fast accepted, which Allaah granted him in the first place.
As for his joy at the time when he breaks the fast, then it is due to the completion of the act of worship and its being free from evil and those things that have been forbidden in it. This is from the praiseworthy types of joy since it is a joy that emanates from the obedience to Allaah and the completion of the fast, due to which great reward has been promised. This is as Allaah says: “Say: By the grace and mercy of Allaah, and by that, then rejoice.” 
4. The breath coming from the mouth of the one fasting is more pleasant in the sight of Allaah than the scent of musk. This beautiful smell will be for the Day of Judgement for that is the day when the rewards for deeds will be manifested. This is based on one narration of the hadeeth: “…more pleasant in the sight of Allaah on the Day of Judgement…” 
Likewise it will be in the life of this world, since that is the time for the manifestation of the signs of worship, due to the report:
“And the scent coming from the mouth of the one fasting when he breaths out from the food (he ate previously) is more pleasant in the sight of Allaah than the smell of musk” 
This scent, although disliked by the people who smell it in this world will, however, be more pleasant in smell in the sight of Allaah than the scent of musk. This is because it is something that originates from the obedience to Allaah.
Ibn Hibbaan (rahimahullaah) said: “The sign that will mark the believer on the Day of Judgement is the brightness (of their faces) due to their ablution (wudoo’) in this world, causing a distinction between them and the rest of the nations. And their mark on the Day of Judgement due to their fasting will be pleasant smelling breath, more pleasant in the sight of Allaah than the scent of musk. This is in order that they may be known amidst that group for that deed. We ask Allaah to grant us blessing on that day.” 
And from the merits of Ramadaan is that Allaah has distinguished those who fast with a specific door from the doors of Paradise. No one more righteous than them will enter through it. Sahl Ibn Sa’ad (radyAllaahu ‘anhu) reported that the Prophet (sallAllaahu ‘alayhi wa sallam) said: “Verily, there is a door in Paradise, which is known as Ar-Rayyaan. On the Day of Judgement, the ones who fasted will enter in through it, no one other than them will enter in through it. And when they have entered, it will close, so no one will enter through it (after them).” 
And in addition to the wording: “And whosoever enters will be given to drink. And whosoever drinks will never feel thirsty again.” 
However, these merits will not be attained except by the one who fasts with sincerity by abstaining from food, drink, intercourse, abstaining from hearing the unlawful, looking towards the prohibited and earning from unlawful means. Thus his body limbs must fast and abstain from sinful acts. His tongue must fast and abstain from lying, foul speech and false swearing. This is the legislated fast, the result of which will be great reward. And if this is not so, then the Prophet (sallAllaahu ‘alayhi wa sallam) has said: “Whosoever does not abandon false speech and acting upon it, then Allaah has no need for him to abandon his food and drink.” 
And Abu Hurairah (radyAllaahu ‘anhu) reported that the Messenger of Allaah (sallAllaahu ‘alayhi wa sallam) said: “Perhaps, all that one who fasts will get from his fast is hunger and thirst. And perhaps all that one who stands at night in prayer will get from his standing is sleeplessness.
-  Al-Bukhaaree (4/103) and Muslim (1151)
-  Surat-uz-Zumar: 15
-  Tafseer Ibn Katheer (7/80)
-  Surah Yoonus: 85
-  This wording is found in the hadeeth of Muslim (Book of Fasting: 163)
-  Reported by Ibn Hibbaan and Ahmad
-  See Saheeh Ibn Hibbaan (8/211)
-  Al-Bukhaaree (4/111) and Muslim (1152)
-  This increase to the hadeeth is found in the Saheeh of Ibn Khuzaimah (no. 1903)
-  Al-Bukhaaree (10/473)
-  Reported by Ahmad, Ibn Hibbaan and others with an authentic chain of narration