As the adage goes, if you can't be a good example, at least be a horrible warning.  Well, in this passage, Moses is a horrible warning for we church people, especially leaders in the church.  

It is because of Moses' failure in this event, the second time God bring water out of a rock, that Moses and Aaron are unable to enter the Promised Land.

What did he do wrong?  He brought judgement where God had extended grace.  He forgot he was the instrument of God's power, rather than the source of that power. He thought he knew how God worked.

Heed the warning, church person...