First of all, let’s look at energy. Every energy have a source, for instance, electricity. It has a generator and it goes down once its source dies.
So it is to everything in the universe. Something caused the Big-Bang and that it is believed in the religious world to be God. However, some scientists believe that God died in the process or that the Big-Bang might have killed him.
Now, consider the Biblical book of Genesis which said God breath into man and he became a living soul after creating other living things other than humans. That one breath has multiplied into thousands and thousands of living souls.
If God dies or had died, there would be no existence of souls or any living thing in the universe. Perhaps the planets, rocks, stars, etc. in the cosmos may still be existing but there would be no energy to drive them as it is happening now. The whole universe would stop expanding and freeze to zero degree.
So since the universe is still living lively, it means the root-source of the energies existing in it is God. That means if God dies, we all die and there will be no life ever again in the whole universe (this includes the frozen possibility of the universe).