Why do they need the leaves of the tree of life for healing?

In Revelation 21 and 22 there are verses about the nations living on the New Earth. It says that they need the leaves of the tree of life for healing. Who are these people? Where did they come from? Do they also have glorified bodies?

This is during the Millenium period.

These are the people who have become believers after the Rapture while on earth - those that have come through the Great Tribulation.

There is the judgement of the sheep and goats and they are the sheep. They live in unglorified bodies still, so still vulnerable to sickness and subject to sin.