Churches across South Africa are to hold prayers for Nelson Mandela, who has been in hospital for four days being treated for pneumonia.
Several hundred people are expected to gather at the Regina Mundi church in Soweto - once a focal point of the struggle against apartheid.
On Saturday, South Africa's presidency said Mandela, 94, was breathing without difficulty.
It said excess fluid had been drained from the lungs to ease his breathing.
There are no details yet on how long he will remain in hospital.
After Mandela was admitted to hospital late on Wednesday, President Jacob Zuma said people "must not panic".
The former president first contracted tuberculosis in the 1980s while detained on windswept Robben Island, reports the BBC.
His lungs are said to have been damaged while working in a prison quarry. This latest spell in hospital is his fourth in just over two years.
Mandela served as South Africa's first black president from 1994 to 1999 and is regarded by many as the father of the nation for leading the struggle against apartheid.
The statement read by presidential spokesman, Mac Maharaj, on Saturday said that Mandela had been admitted to hospital "due to a recurrence of pneumonia".
It said: "Doctors advised that due to the lung infection, former President Mandela had developed a pleural effusion which was tapped. This has resulted in him now being able to breathe without difficulty.
"He continues to respond to treatment and is comfortable."
Meanwhile, five members of the South African military have died in a helicopter crash, officials said.
The aircraft was patrolling the Kruger National Park on Saturday evening looking for rhino poachers.
The patrol was routine and an investigation is under way.
The poaching of rhinos is rampant in South Africa. Their horns are sold in Asia, where some believe they have medicinal purposes, although there is no evidence to support it.
The South African Broadcasting Corporation quoted Brig Gen Xolani Mabanga as saying that the Agusta A1-0-9 light utility helicopter had come down at around 19:00 GMT on Saturday, killing all five people on board.
Gen Mabanga said the ministry of defence extended condolences to the families of the deceased, all members of the South African National Defence Force.