1 Samuel 15:16-18

16Then Samuel said to Saul, “Wait a minute! Let me tell you what the Lord said to me last night.” Saul said to him, “Tell me.”

17Samuel said, “Is it not true that when you were insignificant in your own eyes, you became head of the tribes of Israel? The Lord chose you as king over Israel.

18The Lord sent you on a campaign saying, ‘Go and exterminate those sinful Amalekites! Fight against them until you have destroyed them.’