Allah has assigned a great reward for Hajj Mabrur, as evidenced by the saying of the Messenger (peace be upon him) "There is no reward for Hajj Mabrur except Paradise." (1)
The meaning of birr (from which the word "Mabrur" is derived) involves the following two:
Good behavior towards people, fulfilling ones duties towards others and giving them their rights. In the Hadith, "Al Birr is good behavior." (3) In the Musnad, from Jabir, Marfu` narration states, "They said: 'What makes Hajj Mabrur, O Prophet of Allah (peace be upon him)?' He said, 'providing food to people and spreading (the greeting of) salam'." (4)
Doing much worship and the trait of Taqwa, as opposed to sinfulness. Allah says,
Do you order people towards al-birr (righteousness) while you forget (it) yourselves?
[Noble Quran 2:44]