The fourth pillar of Islam is sawm (i.e. fasting). Allah prescribed fasting upon every able and adult Muslim during the whole of the month of Ramadan, the ninth month of the lunar calendar.
Exempted from the fast are the very old and the insane. On the physical side, fasting starts from the light of dawn to sundown. One has to abstain from food, drink and sexual relations. On the moral, behavioral side, one must abstain from lying, malicious gossip, quarreling and trivial nonsense.
Those who are sick, elderly or on a journey, and women who are menstruating, pregnant or nursing are permitted to break their fast, but they have to make up for the missed fast days later. In case of the physically unable persons, they have to feed a needy person for each day missed. Children should be trained on fasting and observing the prayers. By attaining puberty, fasting becomes a must.
Although fasting is beneficial to the health, it is regarded principally as a method of self-purification. By cutting oneself off from worldly pleasures and comforts, even for a short time, the fasting person gains true sympathy for those who go hungry regularly, and achieves growth in his spiritual life, learning discipline, self-restraint, patience and flexibility.
Furthermore, one is encouraged to recite the entire Qur’an. In addition, special prayer, called Tarawih (night prayer in Ramadan), is held in the mosque every night of the month, during which the Qur’an is recited. These are done in light of the fact that the revelation of the Qur’an to Prophet Muhammad (peace be upon him) began during Ramadan.
During the last ten days of Ramadan, there occurs the Night of Decree (Laylat Al-Qadr). Spending that night in worship is equivalent to a thousand months of worship, i.e. Allah’s reward for it is very great.
On the first day of the following month, after another new moon has been sighted, a special celebration is made, called `Eid Al-Fitr. A quantity of staple food or equivalent money is donated to the poor (Zakat al-Fitr). Everyone has bathed and put on their best, preferably new clothes and communal prayers are held in the early morning, followed by feasting and visiting relatives and friends.
There are other fast days throughout the year. Muslims are encouraged to fast six days in Shawwal, the month following Ramadan, Mondays and Thursdays and the ninth and tenth or tenth and eleventh of Muharram, the first month of the year. The tenth day, called `Ashura’, is also a fast day.
While fasting per se is encouraged, constant fasting, as well as monasticism, celibacy and otherwise retreating from the real world are condemned in Islam. Fasting on the two festival days, `Eid Al-Fitr and `Eid Al-Adha, is strictly forbidden.
Source: Taken from www.islamtomorrow.com with modifications.