The saving Agag alive was in direct violation of the devotion to destruction.

And he took Agag the king of the Amalekites alive,.... This name seems to be a common name of the kings of these people, as Pharaoh was of the Egyptians, see Numbers 24:2. When this king fell into the hands of Saul, he did not put him to death, as he should have done, but preserved him; for what reasons, see in the following verse:

and utterly destroyed all the people with the edge of the sword; that is, all that came in his way, or fell into his hands; all between Havilah and Shur; all excepting those that made their escape, for we after read of Amalekites, and that in large bodies, 1 Samuel 27:8.

Their king, Agag, he took alive (on the name, see at Numbers 24:7), but all the people he banned with the edge of the sword, i.e., he had them put to death without quarter. "All," i.e., all that fell into the hands of the Israelites. For it follows from the very nature of the case that many escaped, and consequently there is nothing striking in the fact that Amalekites are mentioned again at a later period (1 Samuel 27:8; 1 Samuel 30:1; 2 Samuel 8:12). The last remnant was destroyed by the Simeonites upon the mountains of Seir in the reign of Hezekiah (1 Chronicles 4:43). Only, king Agag did Saul and the people (of Israel) spare, also "the best of the sheep and oxen, and the animals of the second birth, and the lambs and everything good; these they would not ban." משׁנים, according to D. Kimchi and R. Tanch. , are לבטן שׁניים, i.e., animalia secundo partu edita, which were considered superior to the others (vid., Roediger in Ges. Thes. p. 1451); and כּרים, pasture lambs, i.e., fat lambs. There is no necessity, therefore, for the conjecture of Ewald and Thenius, משׁמנּים, fattened, and כּרמים, vineyards; nor for the far-fetched explanation given by Bochart, viz., camels with two humps and camel-saddles, to say nothing of the fact that camel-saddles and vineyards are altogether out of place here. In "all that was good" the things already mentioned singly are all included. המּלאכה, the property; here it is applied to cattle, as in Genesis 33:14. נמבזה equals נבזה, despised, undervalued. The form of the word is not contracted from a noun מבזה and the participle נבזה (Ges. Lehrgeb. p. 463), but seems to be a participle Niph. formed from a noun מבזה. But as such a form is contrary to all analogy, Ewald and Olshausen regard the reading as corrupt. נמס (from מסס): flowing away; used with reference to diseased cattle, or such as have perished. The reason for sparing the best cattle is very apparent, namely selfishness. But it is not so easy to determine why Agag should have been spared by Saul. It is by no means probable that he wished thereby to do honour to the royal dignity. O. v. Gerlach's supposition, that vanity or the desire to make a display with a royal slave was the actual reason, is a much more probable one.

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

15:8 All - Whom he found. Now they paid dear for the sin of their ancestors. They were themselves guilty of idolatry and numberless sins, for which they deserved to be cut off. Yet when God would reckon with them, he fixes upon this as the ground of his quarrel.

8, 9. he took Agag . alive-This was the common title of the Amalekite kings. He had no scruple about the apparent cruelty of it, for he made fierce and indiscriminate havoc of the people. But he spared Agag, probably to enjoy the glory of displaying so distinguished a captive, and, in like manner, the most valuable portions of the booty, as the cattle. By this wilful and partial obedience to a positive command [1Sa 15:3], complying with it in some parts and violating it in others, as suited his own taste and humor, Saul showed his selfish, arbitrary temper, and his love of despotic power, and his utter unfitness to perform the duties of a delegated king in Israel.

15:1-9 The sentence of condemnation against the Amalekites had gone forth long before, Ex 17:14; De 25:19, but they had been spared till they filled up the measure of their sins. We are sure that the righteous Lord does no injustice to any. The remembering the kindness of the ancestors of the Kenites, in favour to them, at the time God was punishing the injuries done by the ancestors of the Amalekites, tended to clear the righteousness of God in this dispensation. It is dangerous to be found in the company of God's enemies, and it is our duty and interest to come out from among them, lest we share in their sins and plagues, Re 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.