A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
1 Kings (1 Samuel) 15:1
sa1 15:1SAUL SENT TO DESTROY AMALEK. (Sa1 15:1-6)
Samuel also said unto Saul, The Lord sent me to anoint thee . . .: now therefore hearken thou unto . . . the Lord--Several years had been passed in successful military operations against troublesome neighbors. During these Saul had been left to act in a great measure at his own discretion as an independent prince. Now a second test is proposed of his possessing the character of a theocratic monarch in Israel; and in announcing the duty required of him, Samuel brought before him his official station as the Lord's vicegerent, and the peculiar obligation under which he was laid to act in that capacity. He had formerly done wrong, for which a severe rebuke and threatening were administered to him (Sa1 13:13-14). Now an opportunity was afforded him of retrieving that error by an exact obedience to the divine command.
1 Kings (1 Samuel) 15:2
sa1 15:2Amalek--the powerful tribe which inhabited the country immediately to the eastward of the northern Cushites. Their territory extended over the whole of the eastern portion of the desert of Sinai to Rephidim--the earliest opponent (Deu 25:18; Exo 17:8-16) --the hereditary and restless enemy of Israel (Num 14:45; Jdg 3:13; Jdg 6:3), and who had not repented (Sa1 14:48) of their bitter and sleepless hatred during the five hundred years that had elapsed since their doom was pronounced. Being a people of nomadic habits, they were as plundering and dangerous as the Bedouin Arabs, particularly to the southern tribes. The national interest required, and God, as KING OF ISRAEL, decreed that this public enemy should be removed. Their destruction was to be without reservation or exception.
I remember--I am reminded of what Amalek did--perhaps by the still remaining trophy or memorial erected by Moses (Exo 17:15-16).
1 Kings (1 Samuel) 15:4
sa1 15:4Saul gathered the people together--The alacrity with which he entered on the necessary preparations for the expedition gave a fair, but delusive promise of faithfulness in its execution.
Telaim--or Telem, among the uttermost cities of the tribe of Judah towards the coast of Edom (Jos 15:21, Jos 15:24).
1 Kings (1 Samuel) 15:5
sa1 15:5Saul came to a city of Amalek--probably their capital.
laid wait in the valley--following the strategic policy of Joshua at Ai (Jos 8:4).
1 Kings (1 Samuel) 15:6
sa1 15:6Kenites--(See on Jdg 1:16). In consequence, probably, of the unsettled state of Judah, they seem to have returned to their old desert tracts. Though now intermingled with the Amalekites, they were not implicated in the offenses of that wicked race; but for the sake of their ancestors, between whom and those of Israel there had been a league of amity, a timely warning was afforded them to remove from the scene of danger.
1 Kings (1 Samuel) 15:7
sa1 15:7HE SPARES AGAG AND THE BEST OF THE SPOIL. (Sa1 15:7-9)
Saul smote the Amalekites--His own view of the proper and expedient course to follow was his rule, not the command of God.
1 Kings (1 Samuel) 15:8
sa1 15:8he 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 [Sa1 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.
1 Kings (1 Samuel) 15:10
sa1 15:10GOD REJECTS HIS FOR DISOBEDIENCE. (Sa1 15:10-11)
Then came the word of the Lord unto Samuel, saying, It repenteth me that I have set up Saul--Repentance is attributed in Scripture to Him when bad men give Him cause to alter His course and method of procedure, and to treat them as if He did "repent" of kindness shown. To the heart of a man like Samuel, who was above all envious considerations, and really attached to the king, so painful an announcement moved all his pity and led him to pass a sleepless night of earnest intercession.
1 Kings (1 Samuel) 15:12
sa1 15:12Saul came to Carmel--in the south of Judah (Jos 15:55; Sa1 25:2).
he set him up a place--that is, a pillar (Sa2 18:18); literally, a hand, indicating that whatever was the form of the monument, it was surmounted, according to the ancient fashion, by the figure of a hand, the symbol of power and energy. The erection of this vainglorious trophy was an additional act of disobedience. His pride had overborne his sense of duty in first raising this monument to his own honor, and then going to Gilgal to offer sacrifice to God.
1 Kings (1 Samuel) 15:13
sa1 15:13Saul said unto him, Blessed be thou of the Lord: I have performed the commandment of the Lord--Saul was either blinded by a partial and delusive self-love, or he was, in his declaration to Samuel, acting the part of a bold and artful hypocrite. He professed to have fulfilled the divine command, and that the blame of any defects in the execution lay with the people. Samuel saw the real state of the case, and in discharge of the commission he had received before setting out, proceeded to denounce his conduct as characterized by pride, rebellion, and obstinate disobedience. When Saul persisted in declaring that he had obeyed, alleging that the animals, whose bleating was heard, had been reserved for a liberal sacrifice of thanksgiving to God, his shuffling, prevaricating answer called forth a stern rebuke from the prophet. It well deserved it--for the destination of the spoil to the altar was a flimsy pretext--a gross deception, an attempt to conceal the selfishness of the original motive under the cloak of religious zeal and gratitude.
1 Kings (1 Samuel) 15:24
sa1 15:24I have sinned . . . turn again with me, that I may worship the Lord--The erring, but proud and obstinate monarch was now humbled. He was conscience-smitten for the moment, but his confession proceeded not from sincere repentance, but from a sense of danger and desire of averting the sentence denounced against him. For the sake of public appearance, he besought Samuel not to allow their serious differences to transpire, but to join with him in a public act of worship. Under the influence of his painfully agitated feelings, he designed to offer sacrifice, partly to express his gratitude for the recent victory, and partly to implore mercy and a reversal of his doom. It was, from another angle, a politic scheme, that Samuel might be betrayed into a countenancing of his design in reserving the cattle for sacrificing. Samuel declined to accompany him.
I feared the people, and obeyed their voice--This was a different reason from the former he had assigned. It was the language of a man driven to extremities, and even had it been true, the principles expounded by Samuel showed that it could have been no extenuation of the offense. The prophet then pronounced the irreversible sentence of the rejection of Saul and his family. He was judicially cut off for his disobedience.
1 Kings (1 Samuel) 15:27
sa1 15:27he laid hold upon the skirt of his mantle--the moil, upper tunic, official robe. In an agony of mental excitement, he took hold of the prophet's dress to detain him; the rending of the mantle [Sa1 15:27] was adroitly pointed to as a significant and mystical representation of his severance from the throne.
1 Kings (1 Samuel) 15:29
sa1 15:29the Strength of Israel will not lie--Hebrew, "He that gives a victory to Israel," a further rebuke of his pride in rearing the Carmel trophy, and an intimation that no loss would be sustained in Israel by his rejection.
1 Kings (1 Samuel) 15:31
sa1 15:31Samuel turned again after Saul--not to worship along with him; but first, that the people might have no ground, on pretense of Saul's rejection, to withdraw their allegiance from him; and secondly, to compensate for Saul's error, by executing God's judgment upon Agag.
1 Kings (1 Samuel) 15:32
sa1 15:32Agag came unto him delicately--or cheerfully, since he had gained the favor and protection of the king.
1 Kings (1 Samuel) 15:33
sa1 15:33Samuel hewed Agag--This cruel tyrant met the retribution of a righteous Providence. Never has it been unusual for great or official personages in the East to perform executions with their own hands. Samuel did it "before the Lord" in Gilgal, appointing that same mode of punishment (hitherto unknown in Israel) to be used towards him, which he had formerly used towards others.