In 1970, a rock-cut tomb was discovered by workers building a private house in Jerusalem's Givat Hamivtar neighborhood. Inside the two-chambered burial, dating back to the first century BCE, archeologists found a decorated ossuary – a limestone box containing the bones of the deceased – and an enigmatic Aramaic inscription affixed to the wall. "I am Abba, son of Eleazar the priest," proclaimed the 2,000-year-old text. "I am Abba, the oppressed, the persecuted, born in Jerusalem and exiled to Babylon, who brought back Mattathiah son of Judah and buried him in the cave that I purchased." Who was Abba, this...