2 Thus says the Lord of hosts, 'I will punish what Am'alek did to Israel in opposing them on the way, when they came up out of Egypt.

Matthew Henry's Commentary on 1 Samuel 15:2

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.