South Africa asked the ICJ last week for an urgent order declaring that Israel was in breach of its obligations under the 1948 Genocide Convention in its crackdown against Hamas.
"The State of Israel will appear before the International Court of Justice at The Hague to dispel South Africa's absurd blood libel," spokesman Eylon Levy told an online briefing.
"We assure South Africa's leaders, history will judge you, and it will judge you without mercy," Levy said.
The ICJ, sometimes known as the World Court, is the United Nations venue for resolving disputes between states. Israel's foreign ministry has said the suit was "baseless."
The war was triggered by a cross-border attack by Hamas Islamist militants on Oct. 7, which Israel says killed 1,200 people.
Israel responded with an air and land assault that has killed more than 22,000 people, Palestinian health officials say. While its casualty figures do not differentiate between fighters and civilians, the ministry has said that 70% of Gaza's dead are women and those under 18. Israel disputes Palestinian casualty figures and says it has killed 8,000 fighters.
Levy listed a series of measures Israel's military has taken to minimize harm to non-combatants.
He said Hamas bore full moral responsibility for the war it started and was "waging from inside and underneath hospitals, schools, mosques, homes and UN facilities," Levy said.
He added, without elaborating, that South Africa was complicit in Hamas' crimes against Israelis.
Hamas denies using Gaza's population as human shields.
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