The fifth verse is explaining how until this rapture happens, he's going to help people who help and try to be the best man he can be.
And what'll you do now, my blue-eyed son?"
And what'll you do now, my darling young one?"
"I'm a-goin' back out 'fore the rain starts a-fallin'." I think he's saying that he wants to get out of the world's cruel ways before this apocalypse happens.
"I'll walk to the depths of the deepest dark forest." He'll go to where people need help.
"Where the people are many and their hands are all empty." Where people are hungry and there's no food.
"Where the pellets of poison are flooding their waters." Where there's no clean water due to pollution.
"Where the home in the valley meets the damp dirty prison." Where homes are dirty and sad. They're like prisons because they can't seem to leave.
"And the executioner's face is always well hidden." I interpret this as him say that the government/ authority is usually behind it but you can't get to them.
"Where hunger is ugly, where souls are forgotten." Where people aren't caring about the people that are dying there.
"Where black is the color, where none is the number." I honestly am not quite sure what this means, but it possibly could be that he's going to help black slaves.
"And I'll tell it and think it and speak it and breathe it." I'll tell the world what I think.
"And reflect it from the mountain so all souls can see it." Everyone should see it.
"Then I'll stand on the ocean until I start sinkin'." Then I'll keep helping people until I die.
"But I'll know my song well before I start singin'." I'll know what I'm talking about.
"And it's a hard, it's a hard, it's a hard, it's a hard."
"It's a hard rain's a-gonna fall."