Exodus 17 Amalek war against Israel

Exodus 17
Amalek war against Israel
8 Then Amalek came and fought with Israel in Rephidim.
9 Moses said to Joshua, Choose us men, and go out, fight with Amalek: tomorrow I will stand on the top of the hill and the rod of God in my hand.
10 And Joshua did as Moses told him and fought with Amalek: and Moses, Aaron, and Hur went up to the summit.
11 And it came to pass, when Moses held up his hand, Israel prevailed: and when he let down his hand, Amalek prevailed.
12 But Moses' hands were heavy, they took a stone and put it under him to sit on it: and Aaron and Hur stayed up his hands, one of a band, and the other on; so were his hands steady until the sun set.
13 And so Joshua discomfited Amalek and his people with the sword.
14 And the LORD said unto Moses, Write this for a memorial in a book, and rehearse it in the ears of Joshua; I totally I will scratch the remembrance of Amalek from under the heavens.
15 And Moses built an altar, and called his name, the Lord is my banner.
16 And he said, Because the Lord has sworn, there will be war of the Lord against Amalek from generation to generation.