Exodus 17:12-14

Young's Literal Translation

¹² And the hands of Moses [are] heavy, and they take a stone, and set [it] under him, and he sitteth on it: and Aaron and Hur have taken hold on his hands, on this side one, and on that one, and his hands are stedfast till the going in of the sun;

¹³ and Joshua weakeneth Amalek and his people by the mouth of the sword.

¹⁴ And Jehovah saith unto Moses, `Write this, a memorial in a Book, and set [it] in the ears of Joshua, that I do utterly wipe away the remembrance of Amalek from under the heavens;'