# Come through, come through the gates

The phrase "come through" is repeated to show urgency.

# Build it, build the highway

The word "build" is repeated to emphasize that Yahweh urgently wants the road prepared. The "highway" represents the way the people can return.

# Gather out the stones

"Take the stones out of the road to make it smooth." Stones represent all the obstacles to quick travel. 

# Raise up a signal flag for the nations

A signal flag represents something to draw the attention of others. This means Yahweh is calling the people of the other nations to take notice of the land of Israel and to see what Yahweh has accomplished as he said he would.