Exodus 17:8

6Behold, I will stand before you there on the rock in Horeb. You shall strike the rock, and water will come out of it, that the people may drink.” Moses did so in the sight of the elders of Israel.

7He called the name of the place Massah, and Meribah, because the children of Israel quarreled, and because they tested the LORD, saying, “Is the LORD among us, or not?”

8Then Amalek came and fought with Israel in Rephidim.

9Moses said to Joshua, “Choose men for us, and go out to fight with Amalek. Tomorrow I will stand on the top of the hill with God’s rod in my hand.”

10So Joshua did as Moses had told him, and fought with Amalek; and Moses, Aaron, and Hur went up to the top of the hill.