Imam Al-Bukhari has reported that the Messenger of Allah said: "Paradise has eight gates and one of them is Ar-Rayyan through which none will enter but those who observe fasting." Imam As-Suyooti has reported that Al-Harith Ibn Kalda stated that: "Imposing abstinence from food" was the essence of medicine. Fasting, in medical terms, may mean a variety of things.

Some health care practitioners might recommend juice fasting. This type of fast eliminates all solid foods and the person consumes only fruit and vegetable juices. Others might recommend elimination of all foods except fruits and water for a specified time. Some might even recommend eliminating all foods and drinks for specific periods. The reported purpose for these forms of fasting is to cleanse toxins and poisons from the body and the digestive tract. In Islam, fasting both voluntary and obligatory is an act of worship. Although there may be health benefits, its primary purpose must always be to please Allah.

Alternative medicine considers fasting as a detoxification method. This simply means that it is used to purify the body by eliminating "toxins." This process enhances the healing processes of the body. Fasting generally is perceived to spare any harm to vital organs but uses fatty tissues for energy production. Naturopathic health care practitioners generally proscribe short fasts. Because body temperature may drop during a fast, as does blood pressure, pulse, and respiration, it is considered important to stay warm. Fasting is seen as possible treatment for a variety of disorders and diseases such as obesity, chemical poisoning, arthritis, allergies, psoriasis, eczema, leg ulcers, irritable bowel syndrome, bronchial asthma and even depression.

Fasting is a protection for the body and the mind. Imam At-Tirmithi has reported that the Prophet said: "Fasting and the Quran intercede for a man. Fasting says, 'O my Lord I have kept him away from his food and his passions by day, so accept my intercession for him.' The Quran says, 'I have kept him away from sleep by night so accept my intercession for him.' Then their intercession is accepted." Research has shown that fasting can improve the control of diabetes. Another study has shown that fasting improved the health of persons with irritable bowel syndrome and constipation. Another study suggests that fasting may improve cholesterol levels.

Imam Al-Bukhari has reported that the Messenger of Allah said that Allah, the Almighty Said: "All the deeds of the children of Adam are for them, except fasting, which is for Me and I will give the reward for it." Al-Bukhari has also reported that the Prophet narrated that Allah the Almighty Said: "The fast is for Me and I will give the reward for it, as he (who observes the fast) leaves his (sexual) desire, food and drink for My Sake. Fasting is a shield (from Hell) and there are two pleasures for a fasting person, one at the time of breaking his fast and the other at the time when he will meet his Lord. The smell of the mouth of a fasting person is better in Allah's Sight than the smell of musk."

There are specific requirements for the Muslim to consider when fasting. First is the intention to worship Allah and obey His Commandments. Second, is that the fasting must take place between dawn to dusk. Muslims are prohibited from fasting for more than two continuous days without breaking the fast. This is based on the narration reported in Al-Muwatta, which states that the Prophet forbade fasting for two days or more without breaking the fast in between. Likewise, fasting is prohibited on the following days:

i) 'Eed Al-Fitr: The day of festival after the Ramadan fasting

ii) 'Eed Al-Adh-ha: The 'Festival of Sacrifice' celebrating on the 10th of Dhul-Hijjah, the last month of Islamic Calendar

iii) Days of Jumu'ah (Fridays): If a person needs to fast on the day of Jumu'ah, either he should fast on the prior day of Jumu'ah and continue on the day of Jumu'ah, or he can fast on the day of Jumu'ah but has to continue the fast on the next        day too.  

Married women are admonished not to fast without the permission of their husbands (especially optional fasts), as the husband have a righty over their wives.

Breaking the fast with dates or sips of water is better. Again, this is based on the Prophet's  Sunnah and the narration reported by Imam Abu Dawood : "When one of you is fasting, he should break his fast with dates, but if he cannot get any, then (he should break his fast) with water, for water is purifying." Imam Muslim has reported that the Prophet said: "The Ajwah date is an excellent remedy." The best days for fasting are Mondays and Thursdays. Imam At-Tirmithi also reported that the Prophet said: "The deeds of men are presented to Allah on Mondays and Thursdays, and I like mine to be presented when I am fast­ing." The Ayyam Al-Beedh (the thirteenth, fourteenth, and fif­teenth of each lunar month) are also recommended for fasting.

While both the obligatory fasting dur­ing Ramadan and the voluntary fast­ing during the remainder of the year are acts of worship, they may provide healing to the body. Whatever healing may occur because of fasting is a blessing from Allah; however, this should not be the intention or the goal of fasting. Fasting gives us a greater ability to control our desires and emotions. It should not be con­sidered a "cure-all" or a diet program. Those who fast will receive their reward from Allah as long as their intentions are pure and their fasting is not harmed or nullified by lying, backbiting, or evil deeds.