On the authority of Ibn Omar, the son of Omar bin Al-Khattab, may Allah be pleased with both, who said : I heard the Messenger of Allah (peace be upon him) "Islam has been built on five [pillars]: testifying that there is no god but Allah and that Muhammed is the messenger of Allah, performing the prayers, paying the zakat, making the pilgrimage to the House, and fasting in Ramadan."
[Bukhari]