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 Mr 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 Mr 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.
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.
Mr 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 Mr 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.”
The statement said the presidency “would like to acknowledge and thank all who have been praying for, and sending messages of support for, Madiba and his family.”
Madiba is Mandela’s clan name and is widely used to refer to him.
The hospital Mr Mandela is attending has not been disclosed.