In trying to understand why he published an essay on April 1 in The Washington Post retracting his harshest accusation against Israel and toughening his stand toward Hamas and the United Nations — an essay that has been rejected by the fellow members of his investigation panel — the South African precedent is important. For Mr. Goldstone, it was the model of how the Gaza report would work. Instead, it helped drive Israeli politics farther to the right, gave fuel to Israel’s enemies and brought no notable censure on Hamas.

“I know he was extremely hurt by the reaction to the report,” said Aryeh Neier, president of the Open Society Foundations, who has known Mr. Goldstone for years and remains close to him. “I think he was extremely uncomfortable in providing some fodder to people who were looking for anything they could use against Israel.”

In describing his new position, Mr. Goldstone wrote, “If I had known then what I know now, the Goldstone report would have been a different document.” He has declined requests to elaborate. Interviews with two dozen people who know him suggest a combination of reasons: the hostility from his community, disappointment about Hamas’s continuing attacks on civilians, and new understanding of Israel’s conduct in a few of the most deadly incidents of the war.

The year and a half since the Gaza report was published have been hard on Mr. Goldstone. Hailed by the Arab world and the anti-Israel left, he has been censured by those with whom he had always identified. One of his two daughters, who spent more than a decade in Israel and now lives in Canada with the man she married here, has been furious with him, according to a family friend; he was nearly unable to attend the bar mitzvah of his other daughter’s son in South Africa because of plans by some members of the Jewish community there to demonstrate against his presence.