On the authority of Ibn Omar, the son of Omar bin Al-Khattab, may Allah be pleased with both, who said : I heared the messenger of Allah say :

"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 and Muslim)

Allah says in Surah 12,Verse 76 what can be translated as: Never think that you have reached the final stage of knowledge and nobody knows more than yourself. Remember! Above everyone endowed with knowledge is another endowed with more knowledge.