Jesus warns his disciples and the crowd about the Pharisees. They look good on the outside, but are actually hypocrites. It would be difficult to find Jesus condemning anyone more harshly than this. The problem is that they know the most about the Bible, but use their knowledge for their own gain rather than to honor God.
This kind of condemnation is hard to hear. The Pharisees probably thought they were doing the right thing, but were blinded by their own pride. In what ways could we be trying to do the right things and not know we are looking at things incorrectly? We would all be wise to pray and ask God to let us know if we are blind to some wrong attitude.