Archbishop Joe Seoka used the eve of the sorrow-tinged anniversary to urge South Africans to rally together.
"God is using Madiba, and his extended illness, to present to us a great challenge to unite behind the values that he represents," the Pretoria archbishop said, using Mandela's clan name.
Mandela was rushed to the Pretoria Mediclinic Heart Hospital on June 8 with a recurring lung infection.
The South African presidency reported his condition was still "critical but stable", today.
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Early in his stay family testimony and court documents gave an indication of the seriousness of his condition. He was described as being in a "vegetative state" and depending on life support to survive.
On June 23 the presidency said "the former president's condition had become critical over the past 24 hours," as President Jacob Zuma cancelled a foreign trip.
But since then friends and family members reported the peace icon's health was improving.
Across the country there was an outpouring of charitable deeds, with many people offering 67 minutes of service for the 67 years he was in public service.
But despite recent upbeat assessments, there appears little sign of a much-wished-for discharge from hospital.
Last month US network CBS reported, citing unnamed sources, that Mandela underwent a surgical procedure to unblock a dialysis tube.
It also said that he had two scares, once when he failed to respond to his medications and on another occasion when his life support machine showed him in distress.