Exodus 17:5-6

And Jehovah said unto Moses, Pass on before the people, and take with thee of the elders of Israel; and thy rod, wherewith thou smotest the river, take in thy hand, and go. Behold, I will stand before thee there upon the rock in Horeb; and thou shalt smite the rock, and there shall come water out of it, that the people may drink. And Moses did so in the sight of the elders of Israel.