Eternal Sanatan law
Everything that is created in this world has one limitation: time, duration. You may call it life or existence. Even a stone has a life. After a certain time, that stone will be melted, powdered or destroyed. There is eternal Sanatan law, Sanatan Dharma. It says: who has come, has to go. Who received it, has to give it over. Who was born will die; what is created will be destroyed; what is manifested will disappear. So, everything has its time.
Now, what is the purpose of this all?