Narrated Ibn 'Umar (radiyallaahu 'anhu):
Allah's Messenger (salallaahu 'alaihi wa'sallam) said:
Islam is based on (the following) five (principles):

1.To testify that La ilaha ill-Allah wa anna Muhammad-ar-Rasul Allah
(none has the right to be worshipped but Allah and Muhammad is the Messenger of Allah).

2.Iqaamat-as-Salat [to offer the (compulsory congregational salat (prayers) dutifully and perfectly].

3.To pay Zakat.

4.To perform Hajj (i.e pilgrimage to Makka).

5.To observe Saum [fasts (according to islamic teachings)] during the month of Ramadan.


Sahih Al-Bukhari