It is obligatory according to the Book of Allaah and the Sunnah of His Messenger, sallallaahu ‘alayhi wa sallam, and according to the consensus of the Muslims. The Prophet, sallallaahu ‘alayhi wa sallam, said: “Allaah has enjoined the Hajj upon you, so perform Hajj.” And the Muslims are unanimously agreed upon that. It is something that no Muslim has any excuse for not knowing. Whoever denies that it is obligatory and he is one of those who live among the Muslims, is a disbeliever. A person who fails to do it out of negligence is in grave danger, because some of the scholars said that such a person is a disbeliever.