Narrated by Ibn ‘Umar (R.A):
Allah’s Apostle صلى الله عليه وسلم said: Islam is based on (the following) five (principles):
1. To testify that none has the right to be worshipped but Allah and Muhammad صلى الله عليه وسلم is Allah’s Apostle.
2. To offer the (compulsory) prayers dutifully and perfectly.
3. To pay Zakat (i.e. obligatory charity) .
4. To perform Hajj. (i.e. Pilgrimage to Mecca)
5. To observe fast during the month of Ramadan.
(صحيح البخارى كتاب الايمان)