Then he said to him, “Thus says Adonai: ‘Because you have released out of your hand the man whom I had devoted to destruction, therefore your life will be in place of his life and your people in place of his people.’”
So Saul died because of his unfaithful acts that he committed against the word of Adonai, which he did not keep, and he even consulted a medium for guidance
“But I did obey the voice of Adonai,” Saul said to Samuel. “I went on the mission on which Adonai sent me, and brought back Agag the king of Amalek—and utterly destroyed the Amalekites.
But Saul and the people spared Agag as well as the best of the sheep, the cattle, even the fatlings and the lambs, and all that was good, since they were not willing to utterly destroy them; everything that was worthless and feeble, they destroyed completely.