Samuel said to Saul, Yahweh sent me to anoint you to be king over his people, over Israel: now therefore listen you to the voice of the words of Yahweh.
"Therefore hearken to the words of the Lord.  Thus saith the Lord of hosts  ..."  (1 Samuel 15:1-2).  In this passage, Samuel took every precaution to make it certain that Saul understood that his instructions were not those of the prophet, but were the commandments of God; and there was no reason whatever, why Saul should have failed to believe what Samuel said. The things which Samuel had previously said to Saul had all come true; and any person in his right mind would have had no reason to doubt that what Samuel identified to Saul as God's commandments, were indeed just that.