Numbers 20:8

Take the rod, the same shepherd's staff which had already figured so largely in various miracles, Exodus 17:5, and gather thou the assembly together, thou and Aaron, thy brother, and speak ye unto the rock before their eyes, in an address which was equivalent to a command and must yield results; and it shall give forth his water, and thou shalt bring forth to them water out of the rock; so thou shalt give the congregation and their beasts drink. So the Lord chose to overlook the people's sin of grumbling and to treat them with a kindness which they did not deserve.