Why wouldn’t the “amulet” be a phylactery (Tefillin)? Early Christians were also Jews, or had been Jews. Isn’t this just a phylactery Christian style? Why make it sound like a superstition?
The kingdom of God was an external thing in the Old Testament, the phylacteries for instance, certain scriptures attached to their heads and arms; as opposed to the New Testament which is the kingdom of God internalized, Luke 17:20, 21. i.e., the revelation of Jesus Christ.