Former finance minister Pravin Gordhan is expected to speak at a memorial service for Ahmed Kathrada in Cape Town on Thursday.
Gordhan will speak at the St Georges Cathedral at the second of four memorial services for Kathrada.
Other speakers expected include Anglican Archbishop of Cape Town Thabo Makgoba, and Robben Island veteran Eddie Daniels.
Ahmed Kathrada Foundation CEO Neeshan Balton previously said the organisation was not responsible for organising the events.
"We have merely endorsed them. Different people have opted to choose their own speakers and I think they saw the impact from the memorial service," said Balton.
Several speakers at Kathrada's funeral last Wednesday, and at his memorial service on Saturday, cited an open letter he wrote to President Jacob Zuma in April 2016, calling on him to step down.
Signing off his letter, he wrote, "To paraphrase the famous MK slogan of the time: 'There comes a time in the life of every nation when it must choose to submit or fight.' Today, I appeal to our president to submit to the will of the people and resign."
Senior ANC leaders used the memorial service to voice their dissatisfaction with how Zuma was leading the country.
On Saturday, various leaders spoke up about Zuma's Cabinet reshuffle, in which he sacked Gordhan and his deputy Mcebisi Jonas.
Gordhan called for mass mobilisation and told South Africans to be vigilant and "connect the dots" to determine how money flowed from Treasury to various projects and budgetary needs.