What discovery in the late 1940s contained copies that predate the birth of christ of old testament books?

The discovery of the Dead Sea Scrolls in the late 1940s contains the copies that they predate the birth of Christ of old testament books.
In 1947 Muhammad, a Bedouin shepherd discovered the scrolls in several sealed jars, he collected the best seven scrolls. The scrolls were written in Hebrews. Upon studying, they found eleven caves containing ancient documents and fragments.