Jesus versus the Pharisees. This is what we witness today. For what? As we know Jewish law was very demanding of the individual believer and practice near of Jewish law. There were more than 600 laws the people had to observe every day of their lives. As we consider some of their "person vs law" moments, our modern thinking shrugs the shoulders in amazement and disbelief. Rules for the Sabbath day were and continue to be quite stringent for Orthodox Jews in particular.
Jesus knows what the Pharisees are ready to do if Jesus heals the infirm man. That would be considered work on a Sabbath. Today, for example if a person wants to light a stove on the Sabbath, that is considered a violation of the laws!
Underlying the event in this part of St. Mark's gospel is a teaching about the difference between the law and the spirit of the law. In the times of Jesus, he is teaching that the spirit of the law should be given more understanding. In our modern times perhaps we should consider how our focus might be better aimed at the law itself.