Sforno on Exodus 17:16/ספורנו על שמות י״ז:ט״ז

1ויאמר כי יד על כס י-ה, Moses explains the reason and purpose of his prayer being the fact that G’d Himself had sworn an oath to remain at war with Amalek from generation to generation. If G’d is at war with that nation, we as G’d’s representative on earth, must certainly also be at war with that nation. It is what our sages referred to when they said that three commandments cannot be fulfilled until the Jewish people are securely settled in the land of Israel, 1) appointment of a king; 2) destroying the last vestiges of Amalek; 3) the building of a permanent Temple. Moses therefore had prayed for the time when these three hallmarks of Jewish history could be attained. (Sanhedrin 20)