Exodus 17:3-6

And the people thirsted there for water; and the people murmured against Moses, and said, Wherefore hast thou brought us up out of Egypt, to kill us and our children and our cattle with thirst? And Moses cried unto Jehovah, saying, What shall I do unto this people? they are almost ready to stone me. 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.