Jesus responds to the accusation made against Him by the Pharisees in this verse. He has been accused of having gained His impressive ability to cast out demons from the devil, whom they refer to as Beelzebul. Their foolish accusations might backfire on them and undermine the credibility of their own associates. In Jesus' view, the biggest problem is the hard-hearted stubbornness of the Pharisees towards God.
In some instances, a good 'actor' can appear to exhibit godliness through strict discipline, human programming, or legalistic behavior while denying the Lord Who bought them. As a result, such individuals will bring swift destruction upon themselves because God knows the thoughts and motives that lie behind our words and actions.
Speaking carelessly about the gospel and God is a very serious offense. It is imperative that we all be mindful of the thoughts that we think, the words that we say, and the motives that guide our thoughts, words, and actions in light of this warning. We may never lose our salvation, but we may quench the Spirit, which dishonors God and is detrimental to our well-being.

Dear Heavenly Father, it is sobering to observe how the Scribes and Pharisees were stifled by legalism and pride. Seeing how jealousy and self-conceit can make us distance ourselves from Jesus and prevent us from valuing Him as He deserves is thought-provoking. Please provide me with a teachable attitude and prevent me from developing biased opinions that are in opposition to Your Word. If I have spoken idle words indiscreetly, please forgive me, and may my words and my meditations be righteous before You. 
In Jesus's name I pray. Amen.