The Messenger of Allah (peace and blessings be upon him and his family) said that Allah (most high) said:
“Fasting is Mine and I reward it.”
Shaykh Ahmad ibn Idris al-Fasi said:
“Fasting is Mine and I reward it”: Meaning that fasting is one of My characteristics, as He Most High said, ‘He feeds and is not fed.’ There is a hadith that says “Adopt the qualities of Allah”. He Most High and Transcendent has ordered His slaves to adopt this characteristic, which is to not eat, for a specified period of time. Thus His saying “Fasting is Mine” means: It is in Truth- in Reality- Mine, because I feed and am not fed.
“And I reward it” means: I am its reward. Because he has adopted one of My qualities, so I made his reward: Looking at Me, and so I am his reward. For a man said to the Prophet (peace and blessings upon him and his family), ‘Give me advice,’ and so he said to him: ‘Fast, for it is something that has no equal.’
If the explanation of this hadith was not as such, it would have no meaning- high and exalted is Allah above saying something that has no meaning! For if we took the hadith according to its apparent meaning, fasting would be like all other actions, because all actions are done for the sake of Allah, and He Most High and Transcendent gives their reward.