The Prophet (peace and blessings be upon him) said, “Islam is built upon five pillars: testifying that there is no true god except Allah and that Muhammad is the Messenger of Allah, performing Prayer, paying the Zakah, making the pilgrimage to the Sacred House (Hajj), and fasting the month of Ramadan.” (Reported by Al-Bukhari)
In his famous book Fiqh-us-Sunnah, the late Egyptian scholar Sheikh Sayyed Sabiq (may Allah bless his soul) states: Abu Hurayrah (may Allah be pleased with him) reported that the Prophet (peace and blessings be upon him) said: “The performance of `Umrah is expiation for the sins committed between it and the previous ones. And the reward for Hajj Mabrur (pilgrimage accepted by Allah) is nothing but Paradise.” (Sahih Al-Bukhari, Vol. 3, Book 27, hadith no. 1)
In another Hadith, Ibn Juraij reported on the authority of Jabir (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: “This House of Allah (the Ka`bah) is the pillar of Islam; so whosoever heads for it with the intention of performing Hajj or `Umrah is under Allah’s Protection. If he should die (during this journey), he will be admitted to Paradise, and if he should return home safely, he will return with reward and gain.” (Al-Haythami, Majma` Az-Zawa’id)