Almost every religion has adopted some form of fasting. Prophet Muhammad and the prophets before him all called upon their followers to fast, as the Quran states, “O you who believe! Fasting has been prescribed for you just as it was prescribed for those before you so that you may be pious and learn self-restraint.” (2:183)
Fasting in Islam requires complete abstinence from food, drink (including water), smoking, and sexual activity from dawn until the time of the evening prayer (just after sunset).
Although fasting is recommended on some other significant Islamic dates, it is however, required every day during the month of Ramadan which is the ninth month of the Islamic lunar calendar. The month of Ramadan is revered and honored by all Muslims and it was during this month on a particular night called the “Night of Destiny” (Laylatul Qadr), that the Quran was revealed to the Noble Prophet.
Muslims believe that on this night, every year, God determines the fate of every person for the year to come. Therefore, worshipping on the Night of Destiny is considered, “Better than a thousand months.” (97:3)
Although the exact night of the Night of Destiny is not known, Islamic scholars approximate the date to fall on either the 19th, 21st, 23rd, 25th, or 27th of the month of Ramadan. Therefore, Muslims copiously worship God on these specific nights. The Quran states, “Verily, We have sent it [Quran] down on the Night of Destiny; and what will make you know what the Night of Destiny is? The Night of Destiny is better than a thousand months; He sends down the angels, and the Spirit during it by His will for every matter; Peace! Until the rising of the dawn.” (97:1-7)
As with prayers, the benefits of fasting are innumerable. Fasting strengthens one's willpower, teaches discipline, encourages sympathy for the poor, breaks harmful habits, strengthens one's health, and establishes a sense of religious brotherhood and sisterhood. However, the strongest benefits are spiritual.
Lady Fatima al-Zahra, the daughter of Prophet Muhammad said, “Fasting is to deepen and strengthen one's faith.”
Fasting sharpens the spiritual awareness and inspires a sense of gratitude towards God.
Apart from refraining from food and drink, Muslims are also encouraged, during the month of Ramadan, to give additional charity to the poor and the needy and to feed other people.
source : Discovering Islam /by Imam Sayed Moustafa Al-Qazwini