Jesus is calling his disciples to the follow him on the narrow path that leads to life.  Though this path is hard in a sense, it is well worth it in the end.  One of the dangers on this path is the presence of "false prophets", people who appear to represent God and the truth of Jesus but in the end are misleading whether they know it or not.  Jesus warns his disciples against such people and how they can be recognized and avoided.  Why is this a concern for Jesus?  Why should it be a concern for all who follow Christ?