Exodus 17:10-16

10So Joshua fought the Amalekites as Moses had ordered, and Moses, Aaron and Hur went to the top of the hill. 11As long as Moses held up his hands, the Israelites were winning, but whenever he lowered his hands, the Amalekites were winning. 12When Moses’ hands grew tired, they took a stone and put it under him and he sat on it. Aaron and Hur held his hands up—one on one side, one on the other—so that his hands remained steady till sunset.

13So Joshua overcame the Amalekite army with the sword.

14Then the LORD said to Moses, “Write this on a scroll as something to be remembered and make sure that Joshua hears it, because I will completely blot out the name of Amalek from under heaven.” 15Moses built an altar and called it The LORD is my Banner. 16He said, “Because hands were lifted up against Or to the throne of the LORD, The meaning of the Hebrew for this clause is uncertain. the LORD will be at war against the Amalekites from generation to generation.”