We are only in the second chapter of Mark, and Jesus is already running into problems with the Pharisees. The Pharisees were a main group within Judaism that emphasized obedience to the law – not just to the Ten Commandments, but also to the 613 other laws that had become part of Judaism in the previous few centuries. These extra rules demonstrate how Judaism became a religion about obedience and rules, and not the religion of faith and relationship with the one True God that it had been for Abraham, Isaac, and Jacob.
Because the Pharisees were so focused on rules, when they saw Jesus doing certain things they became upset. The sinners and tax-collectors were seen as unclean, and a good Jew was not supposed to eat with unclean people like that. But Jesus points back to what our religion is to be about, having that faith relationship with our God and sharing that faith with others so that they can have that same type of relationship with the LORD.
Who is this Jesus? Someone who cares more about the lost than doing what other people think is right.