8 He captured Agag, king of Amalek, alive. Everyone else was killed under the terms of the holy ban. 9 Saul and the army made an exception for Agag, and for the choice sheep and cattle. They didn't include them under the terms of the holy ban. But all the rest, which nobody wanted anyway, they destroyed as decreed by the holy ban.
Matthew Henry's Commentary on 1 Samuel 15:8-9
Commentary on 1 Samuel 15:1-9
(Read 1 Samuel 15:1-9)
The sentence of condemnation against the Amalekites had gone forth long before, Revelation 18:4. As the commandment had been express, and a test of Saul's obedience, his conduct evidently was the effect of a proud, rebellious spirit. He destroyed only the refuse, that was good for little. That which was now destroyed was sacrificed to the justice of God.