Among all the acts of worship (furoo-e-deen), Hajj is the only worship, for which a complete surah (Surah Hajj) is revealed in the Holy Quran. Hajj is also mentioned in Surah Ale Imran and Surah Baqarah. Hajj is also the only worship, which, if started, must be completed and can not be left half-done.
Quran: "And the Hajj is incumbent upon mankind for the sake of Allah, for those who can afford to undertake journey to it; and whoever denies, then surely Allah is Self-sufficient, independent of the worlds", Surah Ale Imran, (3:97).
Hadith 1: If Hajj becomes wajib on a person and it is not performed, then he/she will be raised as a Christian or Jew on the day of judgment.
Hadith 2: When a person, on whom Hajj becomes wajib, completes the Hajj properly, his/her sins are forgiven such as if he/she is a newly born person.
Hadith 3: When a person completes a Hajj properly, his/her every dua is accepted for four months.
Moallim No.68(Inside Mina)