When comparing natural religion to God’s religion, we see that natural religion simplifies sin (like “cooties”) when our sinful nature is in fact a mortal disease that only God can cure. Natural religion also follows human traditions instead of using God’s word without modification. Finally, natural religion focuses on the external consequences of sin instead of the internal new man we have been given.
There are truly only two religions in this world. Natural religion is the idea that you have to do good things in order to get good things from a benevolent being. God’s true religion is that he took on human flesh and did all the work for you. The Pharisees in today’s text looked at sin as something that can be avoided completely or removed by doing the right thing. However, both the Old and New Testaments teach that sin begins with having a sinful nature. This is a mortal disease the leads straight to eternal damnation, and so God gave us the cure by being perfect in our place and giving us a new nature. When we fall into natural religion we quickly elevate traditions to the equivalent of God’s saving Word. When we do this with a tradition, then it is no longer useful. Natural religion focus on external things as in what we say and do while God’s true religion gives us a new nature and thereby changes our heart.