for he said, “For a hand was lifted up to the throne of the Lord ¹  – that the Lord will have war with Amalek from generation to generation.” ² 

So Joshua fought against Amalek just as Moses had instructed him; ¹ and Moses and Aaron and Hur went up to the top of the hill.

So Moses said to Joshua, “Choose some of our ¹  men and go out, fight against Amalek. Tomorrow I will stand on top of the hill with the staff of God in my hand.”