Sometimes we do what to us is a little thing, but to someone else, it is big.
God tells Moses to speak to the rock to bring forth water. Instead, Moses hits the rock with his rod and it spewed water. The result was good, but does the end justify the means? Apparently not, when the means is to disobey God. Saul Alinsky said, “If the end does not justify the means, what does?"
It seems like it is the feminine side of God to tell Moses to speak to the rock. Speaking is hard for Moses. And he wanted to show his power (his rod) to his congregation.
The punishment for such an act is that Moses is told that he won't get to go to the Holy Land. This is his lifelong ambition. This is the task given to him by God, and now taken away.
It was the gentle God that told Moses to speak to the rock. It is the mother who speaks to the child. It is the father that uses the rod. Moses was not ready to go to the promised land, because the Jews needed mercy as well as justice. God asked him to display mercy and gentleness toward the rock. Instead, he hit it.