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"The month of Ramadaan in which was revealed the Qur'aan, a guidance for mankind and clear proofs for the guidance and the criterion (between right and wrong), So whoever of you sights (the crescent on the first night of) the month (of Ramadaan i.e, is present at his home), he must observe Sawm (fasts) that month, and whoever is ill or on a journey, the same number [of days which one did not observe Sawm (fasts) must be made up] from other days, Allaah intends for you ease, and He does not want to make things difficult for you, (He wants that you) must complete the same number (of days), and that you must magnify Allaah [i.e, to say Takbir (Allaahu- Akbar; Allaah is the Most Great) on seeing the crescent of the months of Ramadaan and Shawwal] for having guided you so that you may be grateful to Him." [Al-Baqarah (2):185]

Narrated 'Umar bin Al-Khattab:

Once a Jew said to me, "O the chief of believers! There is a verse in your Holy Book Which is read by all of you (Muslims), and had it been revealed to us, we would have taken that day (on which it was revealed as a day of celebration." 'Umar bin Al-Khattab asked, "Which is that verse?" The Jew replied, "This day I have perfected your religion For you, completed My favor upon you, And have chosen for you Islam as your religion." (5:3) 'Umar replied,"No doubt, we know when and where this verse was revealed to the Prophet. It was Friday and the Prophet was standing at 'Arafat (i.e. the Day of Hajj)" [The Book of Faith Volume 1, Book 2, Hadeeth 43]