The Scribes, experts in the Law, in their jealousy accuse Jesus of having an unclean spirit in Him and attribute His power to evil sources. Undeterred by their criticism, Jesus sharply speaks His wisdom. He does not stop here but warns them of their sins, especially the unforgivable sin against the Holy Spirit.
What then is the sin against the Holy Spirit? Mark seems to suggest that it is something to do with attributing Jesus' power not to His divinity and the action of the Holy Spirit acting in and through Him but rather to some external, evil source.
In the first reading we see David also receiving negative criticisms from the Jebusites who doubt the power of his army. He proves them wrong and conquers Jerusalem. His was not mere human strength but the fact that the Lord was with him, lending him divine strength and protection.
Today, we are called to recognize that in doing God's work, we are not to rely on our personal strengths but rather allow ourselves to be empowered by the Holy Spirit. Yes, we might face human criticism even when we have the best of intentions but that would only affect us if we think of ourselves as being in control. If what we do is for the Lord, let us not be deterred by human viewpoints. Let us instead move on with greater reliance on the Lord.
Lord, may Your hand always be upon me and Your arm make me strong.