Fasting the month of Ramadan is an duty and a great worship. It is among the best acts of obeisance. In Fasting there is great reward.Imam al-Bukhari related the hadith-i Qudsi that the Prophet (sall-Allahu ta’ala ‘alaihi wa sallam) said that Allah said: (The reward of every good deed is multiplied from ten up to seven-hundred times–except that of the Fasting–which is usually done in sincerity, will be multiplied by as many times as Allah wills.)
One of the doors of heaven, named ar-Rayyan, is specified for those Muslims who used to fast in this world. On the Day of Judgment it will be opened, and those who used to fast in respect to Allah will be called to enter through that door. Then ar-Rayyan will be closed, and no others will enter through it.
The month of Ramadan is the ninth month of the lunar year. It is the best month of the year, as the night of al-Qadr in Ramadan is the best night of the year. Fasting became an obligation on the Muslims in the second year after the Prophet emigration. Prophet Muhammad (sall-Allahu ta’ala ‘alaihi wa sallam) fasted Ramadan for nine years after which he passed away.
The obligation on the believers of fasting Ramadan is known from the Qur’an and the hadith. It was explicitly stated in Verse 183 of Surat al-Baqarah: (O believers, Fasting are an obligation upon you as it was ordained upon the [Muslim nations] before you–to help you become pious.) Fasting was an obligation upon the nations before the nation [Ummah] of Prophet Muhammad (sall-Allahu ta’ala ‘alaihi wa sallam), however, fasting the month of Ramadan especially is a specification for the nation of Prophet Muhammad (sall-Allahu ta’ala ‘alaihi wa sallam) only.