Firstly: Defining Fasting
Sawm linguistically: is withholding from something.
Sawm terminologically: worshipping Allah, exalted, by withholding from food, drink, and other nullifiers, from fajr until sunset.
Secondly: The Categories of Fasting
Fasting is categorised as either prescribed or prohibited legally:
The first: is the fast that is legally prescribed, and it is further sub-categorised into two:
1. Wajib fasting
Wajib fasting is of two types
- Wajib due to the origin of the law, without a reason from the legally competent. This is the fasting of the month of Ramadan.
- Wajib due to a reason brought about from the legally competent. This is the fast that is performed as expiation, as a vow, or as made up from past days.
2. Mustahabb fasting (voluntary)
It is further sub-categorised into two:
- Unconditional voluntary fasting, which has been textually evidenced without a time restriction.  It is mustahabb at any and all times, except the time of prohibition.
- Conditional voluntary fasting: which has been textually evidenced with a specific time restriction, like the fasting of the six days in Shawwal, Mondays and Thursdays, `Arafah, and the ninth and tenth of Muharram.
The second: is fasting which is legally prohibited, which is further sub-categorised into two:
1. Haram fasting, like fasting the days of Eid.
2. Makruh fasting, like fasting on `Arafah for the pilgrim.
Thirdly: Virtues of Fasting
There are many virtues to fasting which the Qur'an and the Sunnah have come with. Among these are: That Allah, exalted, attributed the act as for Himself alone, saying: "Fasting is for Me, and I reward for it." All the types of patience are enacted in fasting Fasting intercedes for its owner on the Day of Resurrection. It is among the acts for which Allah, exalted, promised forgiveness and a great reward. It is an expiation for sins and mistakes. It is a means of protection from the Hellfire. Abundant fasting is a reason for admittance into Paradise. The changed smell of a fasting person's mouth is better to Allah, exalted, than the scent of musk.
Fourthly: The Wisdom of Legislating Fasting
The benefits of fasting are witnessed by all those with sound intellects and pure dispositions. Allah, exalted, legislated fasting for His slaves out of mercy for them and a means of their protection and salvation.
There is great wisdom in legislating fasting as well as numerous great benefits. Among these are: Fasting is a means to realise consciousness of Allah, exalted. Allowing the fasting person to appreciate Allah's favours upon him. Teaching the self strength of will and resilience. There is great humiliation for the devil in fasting. Fasting allows for kindness and mercy with the destitute. It purifies the body and gives it good health and endurance.