The same love of God that led to the Son's death and resurrection is the same love that defines what it means to live out the reality of the law of God. The only way we can love with God's love is when we have received by grace through faith the credited righteousness of Jesus Christ. Such powerful love is what enables us to love God and our neighbor.
It is in contrast to this marvelous message of Jesus' mission and true identity that He then warns his listeners to be aware of the Pharisees in Mark 12:38-40. Sadly, the traditions of the Pharisees, which in some cases contained such rich teaching of God's Word, ended up adding man-made thinking to Divine truth - resulting in the spiritual blindness of teachers and students alike. When one reads the parallel of Jesus' denouncement of the Pharisees in Matthew 23:13-36, it is clear how spiritually blind the Pharisees and multitudes were. The oppressive system of the Temple System of Jesus' day resulted in many people being oppressed financially and having little to no ability to identify the very God of glory in human flesh.