Specifically John 3:16 -

All Christians believe.

So how are we distinguishing that some who believe will be saved and others won't?

The verse clearly says:

Jhn 3:16 For God so loved the world, that he gave his only begotten Son, that.....

* whosoever 'believeth' in him 'should not perish', but have everlasting life.

Thanks!

The mercy of God is necessary not only when a person repents, but even to lead him to repent, Augustine