Answer:
Man walks over, man walks under, in times of war he burns asunder. What is it?
The shorter I am, the bigger I am. What am I?
Can not be bought, Can not be sold, Even if it's made of gold. What is it?
Who makes it, has no need of it. Who buys it, has no use for it. Who uses it, can't see it. What is it?
Though I am dark Adam married me.
Almost everyone needs it, asks for it, gives it. But almost nobody takes it.