Nelson Mandela's family members gathered to hear Cape Town Archbishop Thabo Makgoba recite a sombre prayer wishing him a "peaceful, perfect, end" as he lay in hospital on life support.
Mandela, a Nobel Peace Prize winner, who spent nearly three decades years behind bars under white minority rule and went on to become South Africa's first black president, was admitted on June 8 with a recurrent lung infection.
During the last 19 days, his family, and the world, have watched as the 94-year-old slipped from stable to a critical condition.
The world now watches and waits for an update on the man who, in defeating apartheid, changed the course of history and inspired millions across the globe.
"May (we) be filled with gratitude for all the good that he has done for us and for our nation, and may (we) honour his legacy through our lives," the Archbishop's prayer read.
"Grant Madiba eternal healing and relief from pain and suffering," it said, referring to Mr Mandela by his clan name.
"Grant him, we pray, a quiet night and a peaceful, perfect, end."
Mr Mandela – who is due to celebrate his 95th birthday on July 18 – has been admitted to hospital four times since December.
Upon his release from jail in 1990 in one of the defining moments of the 20th century, Mandela negotiated an end to apartheid and won the country's first fully democratic elections.
He served a single term as president, guiding the country away from internecine racial and tribal violence, before taking up a new role as a roving elder statesman and leading Aids campaigner.