It is reported on the authority of Taus that a man said to Abdullah son of Umar (RA) . Why dont you carry out a military expedition? Upon which he replied: I heard the messenger of Allah ﷺ say: Verily, al-Islam is founded on five (pillars): testifying the fact that there is no god but Allah, establishment of prayer, payment of Zakat, fast of Ramadan and Pilgrimage to the House.