Exodus 17:16

For he said, Because the LORD hath sworn that the LORD will have war with Amalek from generation to generation.

The Lord has sworn to have war with Amalek from generation to generation, an enduring conflict declared after Israel's victory when they trusted in God's strength. The hand raised against the throne means the attack on Israel was defiance and assault against God and His throne. Amalek was the first nation to attack Israel in the wilderness, falling upon the weak and weary who lagged behind and showing no fear of God. That assault on the weary and defenseless sealed the nation's doom, for God cares for the weak and cruelty against them does not go unnoticed.

Amalek acted from determination to have its own way, mocking God's deliverance of Israel, boasting that Israel's God could not deliver His people, and vowing to destroy them. Israel's murmuring, unbelief, and lack of trust brought and permitted the attack, for God allowed enemies to make war with them so they would learn that their strength came from Him. Israel's victory and destiny rested not on human strength but on trusting God's strength, with God as their acknowledged leader. The victory was commemorated by the name Jehovah-nissi, and the defeat was to be written down, preserved, and rehearsed as a memorial, so that Amalek's hostility and wrong would be remembered as a lasting warning.

After Israel received rest in Canaan, they were to blot out Amalek's remembrance. God marked Amalek's boastful words and appointed destruction by the people they had despised, making their end a warning to all nations of the fate of a proud and powerful nation. Amalek's cruelty, defiance of God, and idolatry brought a sentence of judgment whose execution was delayed four hundred years, during which the Amalekites did not turn from their sins. When the time for its execution came, God commanded Saul to destroy Amalek in fulfillment of the continuing judgment.