There is a kind of bone or organ no bigger than a barley corn called the luz bone or neskvi. Its shape is almost cubic and apparently it lies at the top of the spine, inside the skull underneath the brain. It is described as having within it many intertwined spider-like blood vessels.
It is indestructible and doesn't decay in the grave. The Midrash says that the Roman Hadrian once took a luz and tried to grind it, burn it, and dissolve it in water, to no avail. When he hammered it against an anvil, the hammer and anvil broke.
The future resurrection of the dead will be from this bone... that is, a person will be resurrected from his luz bone. If you destroy this bone during cremation, it is very bad.
Some believe this may occur through technology. Some believe it will be supernatural when the Messiah comes.
This account makes no sense at all to me.
"It is indestructible and doesn't decay in the grave. The Midrash says that the Roman Hadrian once took a luz and tried to grind it,
burn it, and dissolve it in water, to no avail. When he hammered it against an anvil, the hammer and anvil broke."
"If you destroy this bone during cremation"
If he couldn't burn it, how could it be destroyed in cremation?
I personally do not think the ressurrection of the dead will in anyway involve our physical bodies from this planet.
It just doesn't make any sense to me, I believe that our souls will pass onto the next live, our bodies returning to dust.