I Samuel 15-16
Once Shaul has been established as king, the prophet Shmuel tells him that God commands him to wage a decisive war against Amalek, and that he is not to spare anyone or anything.
Shaul spares the women, children, flocks of sheep, and the Amalekite king – seemingly taking spoils and thereby blurring the true purpose of the war, as well as (perhaps) leading the Amalekite king to believe he has not been truly defeated.
God informs Shmuel (who then relays this message to Shaul) that Shaul’s days as king are numbered, and that the Israelite monarchy will be handed to someone else.
Shaul has neglected to put Agag, the Amalekite king, to death, so Shmuel is the one who carries out the task.
When Shmuel comes to kill Agag, Shmuel confronts him and says that he is being brought to justice for bereaving wives by killing their husbands by sword. Does Agag recognize his impending death as a consequence for his actions? Agag’s words to Shmuel do not express remorse. It seems that he merely accepts death as random – easy come, easy go.
I Samuel 30
Later on in Sefer Shmuel, Amalek attacks Ziklag while David and the men are away. Amalek kidnaps the women and children, preparing them for a fate worse than death.
David and the other men weep, but then mobilize to rescue their families. David finds information about the group of Amalekites from an Egyptian who had been a slave of the Amalekites. He is found unconscious, abandoned in a field, without food or water for three days, another testament of the cruel treatment by his Amalekite master who had discarded him when the Egyptian fell ill.
II Samuel 1
The beginning of Shmuel Bet relates how, after the battle in which Shaul and Yonatan die, an Amalekite boasts to King David that he has killed Shaul, expecting a reward from David, whom Shaul had hounded. David reacts with horror and revulsion that the Amalekite would shamelessly agree to kill King Shaul, the “Divinely Anointed One.”