The hajj takes place this year from Nov. 25 to 29, but many of the faithful are already thronging the airport and docks of Jeddah, the main entry point for pilgrims.
It's an event of huge religious significance. Some three million Muslims from all around the world -- Indians and Pakistanis, Nigerians and Bosnians, Arabs and non-Arabs, rich and poor, Sunni and Shia -- will commune, worship, and celebrate the global unity of Islam.
They'll be performing the same set of ritual acts, dressed in exactly the same clothes, all equal in the sight of God. For those who've completed the hajj, it's a lifetime landmark, a transformative religious experience.
In reality, though, there's another reason why the hajj is important -- even if most Muslims would rather it weren't the case.
Today's hajj -- given the widening sectarian rifts within Islam -- is also very much about politics.
To some extent, of course, it's always been that way. The royals in Riyadh have always taken their guardianship of the Two Holy Places in Mecca and Medina as a key to the spiritual and political guidance of the global community of believers. (It should be said, by the way, that though the Saudis invariably evoke the "nonpolitical" character of the hajj, they've also been known to shower pilgrims with literature espousing the benefits of the sere Wahhabi version of Islam that holds inside the kingdom.)
Given this potentially explosive mix of politics and religion, the recent war of words between the governments of Iran and the hajj's Saudi Arabian hosts deserves to be taken seriously.
On Oct. 26, Iran's Supreme Leader, Ali Khamenei, met with officials from the Iranian hajj organizing committee and seized the occasion to rail against alleged past mistreatment of his compatriots during the pilgrimage.
"Such acts are against the unity of Muslims and contribute to the goals and wishes of the U.S. and foreign intelligence services," he said. "The Saudi government should fulfill its duty in confronting these acts."