How it was found
Between late 1946 and early 1947, shepherds searching the cliffs at Qumran, by the Dead Sea, found clay jars hidden in a cave. Inside one was a scroll of the whole book of Isaiah. All 66 chapters, in order.
It is now called the Great Isaiah Scroll, the most famous of the Dead Sea Scrolls.
How old it is
Experts date it to around 125 BC from its handwriting. That is well over a century before Jesus was born, and about 1,000 years older than any copy of Isaiah known before it was found.
Isaiah wrote around 700 BC. The scroll was copied around 125 BC. Jesus was crucified in the early 30s AD. The prophecy was written, copied and stored in a jar before any of it happened.
What Isaiah wrote
Isaiah 53 reads like an eyewitness account of the crucifixion. Here it is, line by line, next to what happened.
"Despised, and the most abject of men, a man of sorrows, and acquainted with infirmity: and his look was as it were hidden and despised, whereupon we esteemed him not."
Isaias 53:3
His own people rejected him. Given the choice, the crowd called for the release of Barabbas instead (John 1:11, Luke 23:18).
"But he was wounded for our iniquities, he was bruised for our sins: the chastisement of our peace was upon him, and by his bruises we are healed."
Isaias 53:5
He was scourged, nailed to the cross, and his side was opened with a spear (Matthew 27:26, John 19:34).
"He was offered because it was his own will, and he opened not his mouth: he shall be led as a sheep to the slaughter, and shall be dumb as a lamb before his shearer, and he shall not open his mouth."
Isaias 53:7
Accused by the chief priests and the elders, he answered nothing (Matthew 27:12).
"And he shall give the ungodly for his burial, and the rich for his death: because he hath done no iniquity, neither was there deceit in his mouth."
Isaias 53:9
He was crucified between two thieves, then laid in the new tomb of Joseph of Arimathea, a rich man (Mark 15:27, Matthew 27:57 to 60).
"...because he hath delivered his soul unto death, and was reputed with the wicked: and he hath borne the sins of many, and hath prayed for the transgressors."
Isaias 53:12
Mark says it outright: "And the scripture was fulfilled, which saith: And with the wicked he was reputed" (Mark 15:28). And from the cross, Jesus prayed for the men killing him: "Father, forgive them, for they know not what they do" (Luke 23:34).
Why this is a big deal
Without the scroll, anyone could claim Christians rewrote Isaiah after the fact to fit Jesus. The Great Isaiah Scroll ends that argument.
Here is a copy of Isaiah, matching ours almost letter perfect, sealed in a jar more than a century before Jesus was born. The prophecy was there first. Then he fulfilled it.