It would seem that this "barbaric practice" is advocated in the Bible as a covenant between God and Abraham. Now I am no Bible expert, but if my memory serves me right God used to entertain himself by messing with Abraham's mind.
"KILL YOUR FIRST BORN SON!"
....as Abraham prepares to comply........
      "WHOA ABRAHAM, I WAS ONLY JOKING! HERE'S A GOAT. KILL IT INSTEAD!"
   From such wonderful exchanges some our religious traditions.