The ordaining of the fast of Ramadan

The obligation of fasting Ramadan was revealed in Shaʿban of the second year of the Hijra, in Allah's words: "So whoever among you witnesses the month, let him fast it." The Prophet ﷺ fasted nine Ramadans, and fasting became the fourth pillar of Islam.

The legislation of fasting came through a wise gradation: the Prophet ﷺ fasted ʿAshura and ordered its fasting; then came the choice between fasting and a ransom — "And upon those who are able, a ransom of feeding a poor person"; then came the firm command: "So whoever among you witnesses the month, let him fast it."

That was in Shaʿban 2 AH, about a month before the Battle of Badr, so the first Ramadan the Muslims fasted was that of the second year, in the seventeenth of which the Great Battle of Badr took place — they joined fasting and jihad.

The Prophet ﷺ fasted nine Ramadans until he met his Lord, and taught his Ummah that fasting is a shield, and that "the month of Ramadan, in which the Qur'an was sent down as guidance for the people," is the opportunity of a lifetime for freedom from the Fire. So Ramadan became the most beloved of months to the Muslims until the Hour comes.