What Is the Greatest Reward of Fasting?
Question

Does the hadith mean that the reward for good deeds when fasting is multiplied more than seven hundredfold, because Allah, may He be exalted, says: “Fasting is for Me and I shall reward for it”?
Praise be to Allah.Except fasting: It is for Me
It is proven in the hadith that Abu Hurayrah (may Allah be pleased with him) said: The Messenger of Allah (blessings and peace of Allah be upon him) said: “Every deed of the son of Adam will be multiplied between ten and seven hundred times. Allah, may He be glorified and exalted, said: Except fasting. It is for Me and I shall reward for it. He gives up his desires and his food for My sake.” (Narrated by Muslim, 1151) 
Scholarly views on the greatest reward of fasting
In their commentaries on this hadith, the scholars stated that what this means is that the reward for fasting is multiplied more than seven hundredfold. We will quote here some of their many comments: 
Abu’l-Walid al-Baji (d. 474 AH – may Allah have mercy on him) said: 
“The virtue of the multiple reward for fasting is that Allah attributed it to Himself, may He be exalted. This implies that it will be more than seven hundredfold.” (Al-Muntaqa Sharh al-Muwatta, 2/74) 
Abu Hamid al-Ghazali (d. 505 AH – may Allah have mercy on him) said: 
“Allah, may He be exalted, says (interpretation of the meaning): “Only those who are patient shall receive their rewards in full, without reckoning” [az-Zumar 39:10]. Fasting is half of patience, so its reward is beyond what one might estimate and give a figure for.” (Ihya ‘Ulum ad-Din, 1/231) 
Ibn al-‘Arabi (d. 543 AH – may Allah have mercy on him) said:
“Our Lord, may He be Blessed and exalted, has told us that the reward for righteous deeds may be multiplied by a factor between one and seven hundred, but He has withheld from us knowledge of the amount of the reward for patience and has kept knowledge thereof to Himself. “Only those who are patient shall receive their rewards in full, without reckoning” [az-Zumar 39:10]. Because fasting is a type of patience, as the one who fasts refrains from physical desires, Allah, may He be exalted, said: “Every deed of the son of Adam is for him, except fasting; it is for Me and I shall reward for it.” The scholars said: The reward (of every deed) will be weighed out and measured out, except the reward for fasting; it will be scooped up by the handful. Hence Malik said: It is patience in bearing the calamities and sorrows of this world, so undoubtedly everyone who delegates his affairs to Allah, bears patiently whatever befalls him, and refrains from whatever is forbidden to him, his reward cannot be estimated. The Lawgiver indicated that fasting comes under this category of patience.” (Ahkam al-Quran, 4/77) 
Al-Qadi ‘Iyad (d. 544 AH – may Allah have mercy on him) said: 
“Moreover, Allah bestows upon whomever He wills whatever He wills of increase up to seven hundredfold, and even beyond that, such as cannot be estimated, as He, may He be exalted, says (interpretation of the meaning): “Only those who are patient shall receive their rewards in full, without reckoning” [az-Zumar 39:10]. And He said: “Except for fasting, for it is for Me and I shall reward for it” after mentioning the seven hundredfold reward for it.” (Ikmal al-Mu‘allim bi Fawaid Muslim, 8/184)
Ibn Rajab (d. 795 AH – may Allah have mercy on him) said: 
“According to the first report [i.e., that is mentioned at the beginning of the answer], the exception of fasting from the deeds that receive a multiple reward means that all good deeds receive a tenfold reward, up to seven hundredfold, except fasting, for the multiplication of its reward is not limited to that; rather Allah, may He be blessed and exalted, may multiply it greatly, without limiting the number. For fasting is a kind of patience, and Allah, may He be exalted, says (interpretation of the meaning): “Only those who are patient shall receive their rewards in full, without reckoning” [az-Zumar 39:10]. Hence it was narrated from the Prophet (blessings and peace of Allah be upon him) that he called Ramadan the month of patience. 
According to another hadith, the Prophet (blessings and peace of Allah be upon him) said: “Fasting is half of patience.” Narrated by at-Tirmidhi. 
Patience is of three types: patience in obeying Allah, patience in refraining from that which Allah has prohibited, and patience in accepting the decree of Allah when it is hurtful. All three types of patience are combined in fasting.” (Lataa’if al-Ma‘aarif by Ibn Rajab, p. 150) 
Ibn al-Mulaqqin (d. 804 AH – may Allah have mercy on him) said: 
“It was said concerning the verse in which Allah, may He be exalted, says (interpretation of the meaning), “No person knows what is kept hidden for them of joy as a reward for what they used to do” [as-Sajdah 32:17] that “what they used to do” was fasting, so they will be rewarded abundantly, without measure. Fasting is singled out for the more than seven hundredfold reward in this hadith.” (At-Tawdih li Sharh al-Jami‘ as-Sahih, 13/28) 
Shaykh as-Sa‘di (d. 1376 – may Allah have mercy on him) said: 
“An exception is made in this hadith for fasting, which Allah says is for Him, and that He is the One Who will reward for it, on the basis of His generosity and kindness, without meaning that the multiple reward for their fasting is like the reward for other deeds. This is something that cannot be expressed; rather He will reward them with that which no eye has seen, no ear has heard, nor has it ever crossed the mind of man. This hadith points out the reason for singling out this reward for fasting, and tells us that the fasting person gives up the desires of his nafs that he is naturally inclined to love and to give precedence to over other things, and that are also necessary for him, but the fasting person gives precedence to love of his Lord over these things, so he gives them up in a manner that no one could know about except Allah, so his love for Allah becomes more important and overwhelms any other natural inclinations, and seeking the pleasure of his Lord takes precedence over attaining his own whims and desires. Therefore Allah singles out fasting as being for Him and has promised that the reward for fasting is with Him. So what do you think of the reward that the Most Gracious, the Most Merciful, the Most Generous, the Bestower of blessings – Whose generosity encompasses all that exists, and He has singled out His close friends for the greatest share of His generosity, and has decreed for them and made available to them the means by which they may attain what He has of reward in a manner that could not cross the mind of any person – how do you think that Allah will reward these sincere fasting people? 
Here the pen must stop (for I have made my point). Joy will fill the heart of the fasting person for having done an act that Allah has said is for Him, and has made its reward commensurate with His generosity and kindness. That is the grace of Allah that He bestows upon whomever He will, and Allah is the Possessor of great bounty.” (Bahjat Qulub al-Abrar, p. 94-95) 
Shaykh Ibn ‘Uthaymin (d. 1421 AH – may Allah have mercy on him) said:
“The reward for acts of worship is tenfold up to seven hundredfold, up to many times more, except fasting, for it is Allah Who will reward for it. What that means is that the reward for it is very great indeed. The scholars said that this is because fasting combines three types of patience, namely patience in obeying Allah, patience in refraining from disobeying Allah, and patience in accepting His decree. It is patience in obeying Allah because the individual is patient in doing this act of obedience. It is patience in refraining from disobeying Him because he avoids that which is prohibited for the fasting person. And it is patience in accepting the decree of Allah because the fasting person experiences the pain of thirst, hunger, tiredness and lack of energy. Hence fasting is one of the most sublime forms of patience, because it combines the three types of patience, and Allah, may He be exalted, says (interpretation of the meaning): “Only those who are patient shall receive their rewards in full, without reckoning” [az-Zumar 39:10].” (Ash-Sharh al-Mumti‘, 6/458) 
And Allah knows best.