To quote from the website:
'The documents focus on Israel's mobilization in the international protest campaign to prevent the South African government from imposing the death sentence on Mandela during the Rivonia Trial in 1964. Israel also called on South Africa to stop the trial and to abolish the apartheid regime
The Israel State Archives holds a document (not released for publication) showing that Mandela (under an assumed identity) met with an unofficial Israeli representative in Ethiopia as early as 1962. He had fled South Africa in 1961, and visited several African states, including Ethiopia, Algeria, Egypt and Ghana. The Israeli representative in Ethiopia was not aware of Mandela's true identity. Instead the two discussed Israel's problems in the Middle East, with Mandela displaying wide-ranging interest in the subject. Only after his arrest in 1962, on his return to South Africa, did Israel learn the truth....'At the ensuing show trial of Mandela and seventeen other leaders of the ANC, who were accused of plotting violence against the apartheid regime, the prosecution demanded the death sentence (hanging) for Mandela and a number of the other defendants.
As the website informs us, about a third of the defendants at the trial were Jews, and for that and other reasons the Israeli government took a keen interest in the trial and the fate of the accused:
'The South African government addressed this issue by appointing a Jewish lawyer Percy Yutar, deputy general prosecutor of the province of Transvaal, as chief prosecutor in the case to offset accusations of antisemitism. The second reason for Israeli interest in the trial was its desire to strengthen ties with black African nations, who naturally rejected the apartheid regime in South Africa. Another contributing factor to Israel's stand was then Foreign Minister Golda Meir's opposition to racism and discrimination. She herself invested a large amount of time and attention to developing ties with African countries.'Israel's chargé d'affaires in Cape Town told Mrs Meir that in his opinion Israel should inaugurate an international protest campaign to prevent Mandela and the other defendants from receiving the death sentence. Consequently, the philosopher Martin Buber and author Haim Hazaz issued a declaration to the South African government to release the defendants: "You will not silence their voices by hanging them. Their words will ring a thousand times more loudly if you do".
The death penalty was not given, Mandela and five other major defendants being sentenced instead to life imprisonment. Golda Meir reiterated Israel's robust opposition to apartheid, praised Mandela's brilliance at the trial, and noted that the declaration by Buber and Hazaz "undoubtedly expressed" the sentiments of all Israelis.
To see the documents in question and read more go here