The Sons of Thunder, James and John, wanted to call fire down on inhospitable Samaria.  They wanted to kill them and get them out of the way.  They could have cited OT precedence for doing so, but Jesus revealed that this would not be the way His Kingdom citizens would react.  This was contrary to the Spirit of Jesus.  It indicated some other attitude and spirit at work in His disciples.

“But He turned and rebuked them, and said, ‘You do not know what manner of spirit you are of.  For the Son of Man did not come to destroy men’s lives but to save them.’ And they went to another village.’” Luke 9:55-56 (NKJV)