151 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 will punish the Amalekites for what they did in opposing the Israelites when they came up out of Egypt. 3 Now go and attack Amalek, and utterly destroy 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 foot soldiers, and ten thousand soldiers of Judah. 5 Saul came to the city of the Amalekites and lay in wait in the valley. 6 Saul said to the Kenites, "Go! Leave! Withdraw from among the Amalekites, or I will destroy you with them; for you showed kindness to all the people of Israel when they came up out of Egypt." So the Kenites withdrew from 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.