Jesus spoke this parable regarding faith after they were unable to cast the devil out of a man's son, so the man took his son to Jesus whom cast out the devil the same hour and rebuked the unbelief and told his disciple's this parable. The parable is ver significant to the Christian and one need to comprehend it's importance; it was spoken for a purpose and that purpose is revealed in this work (Book) the word "Significant" according to the Merriam-Webster...