God tempts Abraham by asking him to kill his son as a sacrifice. So Abraham does. Fortunately an angel intervenes and stops him. They find a ram caught in a bush and sacrifice it instead. All is well. Abraham is then told that his brother Nahor has had 8 children, one of whom has Rebekah, who will be important to the story later.
In other words:
God asks Abraham to kill his only son as a test. Abraham passes this test and doesn’t have to kill his son.
What I think really happened:
Again, it appears that Abraham is schizophrenic or something. These are the sort of things a schizophrenic hears and is compelled to act on without question.
Moral lesson learned:
Don’t leave your children alone with a crazy person (Genesis 22: 9)