1 Samuel 15:8

And he took Agag the king of the Amalekites alive, and utterly destroyed all the people with the edge of the sword.

The destruction of the Amalekites was God's judicial sentence for their attack on Israel in the wilderness and for their continued persistence in sin, defiance of God, and idolatry, whose execution had been delayed for four hundred years. Saul destroyed the Amalekite people with the edge of the sword but took Agag their king alive, contrary to the command to destroy all. In sparing Agag while destroying the people he carried out the command only in part, in selective obedience that failed to follow God's command fully.

Along with Agag he spared the best of the cattle and destroyed only what he counted as worthless, with the keeping of the cattle excused on the claim that they would be sacrificed to God. Sparing Agag was driven by ambition for renown and prestige, to make the victory appear more impressive by bringing home a royal captive. By sparing Agag in disobedience to God's explicit command he put his own judgment above God's direction and led his people to feel they could do the same.

His failure to carry out God's sentence of justice against Amalek kindled God's wrath against him. His course parallels one who denies wrongdoing until the facts are undeniable, yet still does not confess sin and instead considers himself mistreated. The act shows that prosperity for individuals and for a nation depends on strict adherence to the command of God who sees the end from the beginning, that loyalty to God is proved by unquestioning obedience, and that in deciding any course the question is not whether harm can be seen to result from it but whether it is contrary to the will of God.