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. 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. Now go and strike Amalek and devote to destruction all that they have. Do not spare them, but kill both man and woman, child and infant, ox and sheep, camel and donkey.’” (1 Samuel 15:1-3)

…

And Saul defeated the Amalekites from Havilah as far as Shur, which is east of Egypt. And he took Agag the king of the Amalekites alive and devoted to destruction all the people with the edge of the sword. But Saul and the people spared Agag and the best of the sheep and of the oxen and of the fattened calves and the lambs, and all that was good, and would not utterly destroy them. All that was despised and worthless they devoted to destruction. (1 Samuel 15:7-9)

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And Samuel came to Saul, and Saul said to him, “…I have performed the commandment of the Lord.” And Samuel said, “What then is this bleating of the sheep in my ears and the lowing of the oxen that I hear?” Saul said, “They have brought them from the Amalekites, for the people spared the best of the sheep and of the oxen to sacrifice to the Lord your God, and the rest we have devoted to destruction.” (1 Samuel 15:13-15)

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And Samuel said, “Has the Lord as great delight in burnt offerings and sacrifices, as in obeying the voice of the Lord? Behold, to obey is better than sacrifice, and to listen than the fat of rams.” (1 Samuel 15:22)

But look at what happens seven chapters later, and especially the similar wording:

And [Saul] the king said, “You shall surely die, Ahimelech [the priest], you and all your father’s house.” … And Nob, the city of the priests, he put to the sword; both man and woman, child and infant, ox, donkey and sheep, he put to the sword. (1 Samuel 22:16,19)

Saul had been rejected by God, and he certainly brought about his own fall in trying to protect himself from David, who wasn’t even hunting him. Whoever wrote 1 Samuel clearly knew it, and the choice of wording only emphasizes how far Saul had gone.