Exodus 17:10

7 and he calleth the name of the place Massah, and Meribah, because of the `strife` of the sons of Israel, and because of their `trying` Jehovah, saying, `Is Jehovah in our midst or not?`

8 And Amalek cometh, and fighteth with Israel in Rephidim,

9 and Moses saith unto Joshua, `Choose for us men, and go out, fight with Amalek: to-morrow I am standing on the top of the hill, and the rod of God in my hand.`

10 And Joshua doth as Moses hath said to him, to fight with Amalek, and Moses, Aaron, and Hur, have gone up [to] the top of the height;

11 and it hath come to pass, when Moses lifteth up his hand, that Israel hath been mighty, and when he letteth his hands rest, that Amalek hath been mighty.

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.