A riddle - What is old that kills?

[***]

The first person that gets it right then I would choose them as best answer.

 

[The Random's]

murder?
age?
death?

 

[????? ????? ?????]

I'm gonna go ahead and go with what Cecil said

 

[Capt' Midnight]

Pneumonia.'

 

[Hellfire]

The flow of time.

 

[Jess C]

The Grim Reaper?