151 And Samuel said to Saul, "The Lord sent me to anoint you king over his people Israel; now therefore listen to the words of the Lord. 2 Thus says the Lord of hosts, 'I have noted what Amalek did to Israel in opposing them on the way when they came up out of Egypt. 3 Now go and strike Amalek and devote to destruction[1] all that they have. Do not spare them, but kill both man and woman, child and infant, ox and sheep, camel and donkey.'" 4 So Saul summoned the people and numbered them in Telaim, two hundred thousand men on foot, and ten thousand men of Judah. 5 And Saul came to the city of Amalek and lay in wait in the valley. 6 Then Saul said to the Kenites, "Go, depart; go down from among the Amalekites, lest I destroy you with them. For you showed kindness to all the people of Israel when they came up out of Egypt." So the Kenites departed from among the Amalekites.
Matthew Henry's Commentary on 1 Samuel 15:1-6
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.