2 Kings 13:20-21 (NKJV)
Then Elisha died, and they buried him. And the raiding bands from Moab invaded the land in the spring of the year. So it was, as they were burying a man, that suddenly they spied a band of raiders; and they put the man in the tomb of Elisha; and when the man was let down and touched the bones of Elisha, he revived and stood on his feet.
Elisha and Elijah were two incredible, miracle working prophets of God. A lot of people think the Bible is full of miracles but actually miracles are somewhat rare in the Bible. There are only twelve people who performed miracles in the Bible: Moses, Joshua, Samson, Samuel, Elijah, Elisha, Isaiah, Jesus, Peter, Paul, Stephen and Philip. This one about a dead man walking after touching Elisha's bones is a doozy. It does demonstrate one unmistakable point, that it is not the man but rather God who does the miracles.
The purpose of miracles is to confirm, corroborate, and authenticate the message of God given through his prophets. This one was no less so. It confirmed in a dramatic way that even though God's man Elisha was dead, God is still alive and will still follow through on the truth imparted through Elisha.