The oldest complete copy of a Bible book was found in a Judean cave in 1947

In the winter of 1946-47, a Bedouin shepherd named Muhammed edh-Dhib found a cave in the cliffs above the Dead Sea. Inside were tall clay jars, and inside some of the jars, wrapped in linen, were leather scrolls. Accounts of that first day differ in the details, including the famous stone thrown into the dark to see what was there, but not in the result: seven scrolls came out of what is now called Cave 1 at Qumran, and they passed through a Bethlehem antiquities dealer to scholars in Jerusalem.

One of the seven was a complete copy of Isaiah: seventeen sheets of leather sewn into a roll about 24 feet long, all 66 chapters in 54 columns. Its handwriting dates it to roughly the second century BCE, and radiocarbon tests broadly agree. Before 1947, the oldest manuscripts behind printed Hebrew Bibles were medieval: the Aleppo Codex from about 930 CE and the Leningrad Codex from 1008. The scroll from the cave was about a thousand years older.

That gave scholars something they had never had: a way to compare the medieval text with a copy made a thousand years before it. The scroll differs from the medieval text in thousands of small ways, mostly spelling, and in a number of readings that some modern translations now adopt or footnote. But it is recognizably the same book, chapter for chapter. The scribes who copied Isaiah across those thousand years, with no copy this old to check against, had done their work with remarkable care.