Pope Francis will meet a revered Shiite leader and make history with a message of coexistence in Iraq, a country plagued by bitter divisions.
The opinions Ayatollah Ali Al Sistani hold powerful sway on the Iraqi street and beyond. And their meeting will resonate across Iraq, even crossing borders into neighbouring Iran.
Pope Francis and Mr Al Sistani are to meet on Saturday for at most 40 minutes, part of the time alone except for interpreters, in the latter’s modest home in the city of Najaf.
Who is Grand Ayatollah Ali Al Sistani?
Originally from the Iranian city of Masshad, Mr Al Sistani is the most important Shiite cleric in Iraq.
He moved to Najaf in 1952 where he studied with some of the era's most prominent thinkers, eventually becoming part of the senior clerical leadership, called Hawza, in 1993.
Mr Al Sistani rose to international prominence after the fall of dictator Saddam Hussein in 2003. During the dictatorship he spent some time under house arrest.
A year later he brokered a truce between US and Iraqi forces and fighters loyal to Moqtada Al Sadr, ending the battle of Najaf.
Mr Al Sistani has advocated a separation of religion and the state in Iraq.
Today, many in the Muslim world look to him for advice on daily life and politics.
Mr Al Sistani is also reclusive. In January 2020 his office announced he had undergone surgery for a broken thigh bone, in a rare outing from his home.
He does not make public appearances and his sermons are delivered by representatives. He rarely receives foreign dignitaries.
L-shaped sofas and no shoes: how the pair will meet
Each minute of Saturday’s meeting will probably unfold as meticulously as a scripted stage play.
The convoy of Pope Francis, 84, will pull up along Najaf’s busy, column-lined Rasool Street, which ends at the Imam Ali Shrine.
To the side is an alleyway too narrow for cars. Here, Pope Francis will walk the 30 metres to Mr Al Sistani’s modest home, which the cleric has rented for decades.
Waiting to greet him at the entrance will be the Mr Al Sistani's influential son, Mohammed Ridha.
Inside, and some steps to the right, Mr Al Sistani and the Pope will come face to face, and each will make a simple gesture of mutual respect.
The Pope will remove his shoes before entering Mr Al Sistani’s room.
The host, who normally remains seated for visitors, will stand to greet the Pope at the door and walk him to an L-shaped blue sofa, inviting him to take a seat.
He will stand despite his fragile health, said religious officials. Since fracturing his thigh, Mr Al Sistani has been firmly ensconced indoors. Pope Francis suffers from sciatica.
He will be offered tea and gifts will be exchanged.
It is not clear what Najaf will bestow, but Pope Francis will almost certainly present Mr Al Sistani with bound copies of the Pontiff's most important writings.
Top among them his latest encyclical, Brothers All, about the need for greater fraternity among all peoples to bring about a more peaceful, ecologically sustainable and just world.