Because thou obeyedst not the voice of the LORD, nor executedst his fierce wrath upon Amalek, therefore hath the LORD done this thing unto thee this day. Nor executedst his fierce wrath upon Amalek - See 1 Samuel 15:1-9 (note) and the notes there.
Related Commentaries of 1 Samuel 28:18
1 Samuel 28:18
18 Because thou obeyedst not the voice of the LORD, nor executedst his fierce wrath upon Amalek, therefore hath the LORD done this thing unto thee this day.