This was probably an old formula, the sense of which, on its ethical side, is comprised in the first and second commandments.
Shall be utterly destroyed - The Hebrew word here used is חרם châram (i. e. devoted). See Leviticus 27:28.
Related Commentaries of Exodus 22:20
Exodus 22:20
20 He that sacrificeth unto any god, save unto the LORD only, he shall be utterly destroyed.