Suetonius, The Deified Julius (Divus Iulius)

Suetonius was a Roman biographer and imperial secretary whose Lives of the Twelve Caesars, written under Hadrian around 121 CE, remains the fullest surviving ancient biography of Julius Caesar and his successors down to Domitian. Each life follows a consistent structure, and the Divus Iulius closes with a cluster of omens said to have preceded Caesar's death, among them the haruspex Spurinna's warning after an unfavourable sacrifice that danger to Caesar's life would not extend past the Ides of March, and the exchange between the two men on the morning of 15 March 44 BCE. Suetonius wrote roughly a hundred and seventy years after the events he describes, drawing on earlier written sources and archival material rather than eyewitness testimony, and modern scholarship reads the shaping of his omen clusters as a deliberate structural convention of the biography genre rather than as neutral reportage. Use it for the tradition's own account of the warning as it was told; read the modern scholarly source alongside it for how far that telling can be trusted as contemporaneous.