The word sawm is the Arabic equivalent for fasting; it means "to abstain." Sawm in Islamic practice signifies the conscious abstinence from the cravings of the carnal soul by willingly abstaining from food, drink, and sexual intercourse from the break of dawn until sunset in order to maintain spiritual discipline and self-control.

Fasting was enjoined in Shaban (the eighth month in the Islamic calendar) of the second year after the Messenger's emigration to Medina. 

Observing the fast in the month of Ramadan (the ninth month in the Islamic calendar) is one of the five pillars of Islam; it is enjoined in the Qur'an, and is therefore obligatory. In the Qur'an, issues are handled in a general way. It is the Prophet Muhammad who provided detailed explanations of the Islamic decrees mentioned in the Qur'an, for it is he who is the foremost and greatest interpreter of the Holy Book. The Qur'anic evidence for the necessity of fasting is in the following verse:

O, you who believe! Prescribed for you is the fast, as it was prescribed for those before you, so that you may deserve God's protection (against the temptations of your carnal soul) and attain piety. (Baqara 2:183)

This verse also alludes to the fact that fasting was a practice ordained upon believers before the advent of Islam. Its origins can be traced back to the earliest recorded religions. In spite of some differences associated with the practice of fasting in various belief systems, fasting as an institution for spiritual reasons is common to all religions and well established in Judaism and Christianity. The Bible mentions that Jesus, Moses, Daniel, Elijah, and David, peace be upon them, all fasted. Moses received the Law after fasting for forty days. Similarly, Jesus fasted for forty days in the wilderness before he was called to his ministry. Prophet David fasted every other day. This fast of David is one of the most virtuous of the recommended fasts in Islam as well. Although no longer practiced by most Christians, fasting is observed in one form or another by Roman Catholics, Orthodox Christians, and in most Protestant denominations , where it is perceived as a personal spiritual experience.

The only goal of fasting in Islam is to seek God's pleasure by obeying His Command. It is far beyond restricting food intake or purifying the body of toxins. Fasting helps Muslims attain piety as a means to be in constant awareness of God, doing good, and guarding oneself against evil.

People who are temporarily sick or traveling may break their fasts, but they must make up the days they missed. Menstruating women and women bleeding after childbirth do not fast, and they must make up the days they missed. People with chronic illnesses should feed a poor person for each day they miss, and they do not have to make the missed days. Scholars agree that pregnant women and breastfeeding women who fear for their own health or the health of their children may forego fasting as long as their conditions persist. Scholars differ whether they must make up the missed days or feed a poor person.

Fasting reduces one's desires. It trains a person in self-restraint. He becomes accustomed to keeping a watch on himself. If one can forgo what is normally lawful for a limited amount of time, one should be able to forgo what is always unlawful. It shifts the focus of one's attention from bodily needs to spiritual needs. This focus is complemented in Ramadan by the exhortation to spend more time reading Qur'an and performing extra prayers. For the fast to be rewarded, refraining from food and drink must also be accompanied by refraining from unlawful acts. The Prophet said, "Whoever does not give up forged speech and evil actions, God is not in need of their leaving their food and drink."[1]

Feeling the pangs of hunger should also make a person empathize with those who feel hungry not as a matter of choice but because they can't find enough to eat. Thus Ramadan becomes a month of giving charity as well as fasting.

Fasting is obligatory on healthy, adult Muslims only in Ramadan. However, there are a number of other days when it is recommended, such as three days at the middle of each month, and every Monday and Thursday. Regular fasting helps to maintain the state of mind achieved in Ramadan.

Ramadan is the month in which the Qur'an (began to be) revealed, providing guidance for human beings, with clear verses to guide and to distinguish right from wrong; therefore whoever witnesses that month shall fast it, and whoever is sick or on a journey, the same number of days which one did not observe fasts must be made up from other days. God desires ease and does not desire difficulty for you, that you may complete the total number of fasting days; glorify Him in that He has guided you and that you may give thanks. (Baqara 2:185)