1 Samuel 15:20-21 NKJV

And Saul said to Samuel, “But I have obeyed the voice of the LORD, and gone on the mission on which the LORD sent me, and brought back Agag king of Amalek; I have utterly destroyed the Amalekites. But the people took of the plunder, sheep and oxen, the best of the things which should have been utterly destroyed, to sacrifice to the LORD your God in Gilgal.”

Consider the incident where King Saul had sinned. Samuel had given Saul the commission and conveyed the divine instruction to destroy everything after the victory over the Amalekites, also the herds.