Sahih muslim:16b Chapter: Explaining Al-Iman (Faith), Al-Islam, and Al-Ihsan, and The Obligations of Al-Iman With Affirmation of The Qadar of Allah, Glorious And Most High is He. And Explaining The Evidence For Declaring One’s Innocence Of One Who Does Not Believe In Al-Qadar, And Having A Harsh View Of His Case Book 1, Hadith 20

It is narrated on the authority of (‘Abdullah) son of ‘Umar, that the Prophet (may peace of Allah be upon him) said: (The superstructure of) al-Islam is raised on five (pillars), i. e. Allah (alone) should be worshipped, and (all other gods) beside Him should be (categorically) denied. Establishment of prayer, the payment of Zakat, Pilgrimage to the House, and the fast of Ramadan (are the other obligatory acts besides the belief in the oneness of Allah and denial of all other gods).