When you quench a fire, you put out the fire. When you quench your thirst, your thirst goes away. The word “spirit” here could refer to the Holy Spirit, or one’s own personal spirit. Either way, spirit is the source of all things spiritual. So the basic meaning of the command is not to put out the source of all things spiritual.
Being a disciple of Jesus means being committed to Jesus and His values by 1) listening and following Jesus as my spiritual leader, 2) participating in the church, Jesus’ instrument to address concerns in the world, and 3) caring about other people in both physical and spiritual ways. The listener should be able to understand and relate what it means to be a disciple of Jesus. This sermon is designed to develop a deeper sense of commitment to Jesus and His values.