Exodus 17:5-6

And the LORD said to Moses, “Go on before the people, and take with you some of the elders of Israel. Also take in your hand your rod with which you struck the river, and go. Behold, I will stand before you there on the rock in Horeb; and you shall strike the rock, and water will come out of it, that the people may drink.” And Moses did so in the sight of the elders of Israel.