Explaination- a river runs/flows doesnt walk, murmers/splashes never talks, has a river bed doesnt sleep,has a river mouth(where water comes from) but never eats.
Explaination- The man who invented the coffin doesn't need it (yet) because he is'nt dead. The man who bought it (a alive man) doesn't need it.The man who needs it (a dead man) doesnt know that he actually needs it.