Charles Ellicott Commentary 1 Samuel 15:1-3

"And Samuel said unto Saul, Jehovah sent me to anoint thee to be king over his people, over Israel: now therefore hearken thou unto the voice of the words of Jehovah. Thus saith Jehovah of hosts, I have marked that which Amalek did to Israel, how he set himself against him in the way, when he came up out of Egypt. Now go and smite Amalek, and utterly destroy all that they have, and spare them not; but slay both man and woman, infant and suckling, ox and sheep, camel and ass." — 1 Samuel 15:1-3 (ASV)

(1 Samuel 15:1–3) Samuel also said unto Saul ... —The compiler of the history, selecting, no doubt, from ancient state records, chose to illustrate the story of the reign and rejection of Saul by certain memorable incidents as good examples of the king’s general life and conduct. The incidents were also selected to show the rapid development of the power and resources of Israel at this period.

The sacred war with Amalek is thus introduced without any “note of time.”

The Lord sent me to anoint thee. —The account of the Amalekite war is prefaced by the solemn words used by the seer when he came to announce the Eternal’s will to Saul. They are quoted to show that the war was imposed upon Israel in a general official way by the accredited prophet-messenger of the Most High.