[vouwfietsman]

As already mentioned, empathy.

You are referencing the age old argument of moral origins, you can simply google to find out many sides of the argument (example: https://www.quora.com/If-not-for-religion-where-do-morals-an...).

However, its quite simple to resolve. The gist of it is: if you need a deity holding judgement over you to distinguish right from wrong, you are probably a psychopath.