The Early Church believers came from two different backgrounds: Jews who knew God's law, and Gentiles who had little knowledge of what displeased Him.  The Jews were tempted to look down on Gentiles, but Paul said that they were wrong to do so.  Knowing what is right does not make people holy, if they fail to do it.  And criticising others can never make the critic holy.  And anyway, hidden evil desires are as bad as visible sins (Matthew 5:21-22; Matthew 5:27-28).

It is easy to criticise others when we see their obviously bad behaviour; but it is hard to see the wickedness inside our own hearts (Jeremiah 17:9).  Of course, God sees everything - including the desires and motives that lead us into sin, and only He can help us to recognise our own sinfulness and help us do something about it.  King David knew he needed that help, which is why he prayed, "Search me, God, and know my heart; test me and know my anxious thoughts.  See if there is any offensive way in me, and lead me in the way everlasting." (Psalm 139:23-24).  

Paul is preparing his readers to understand the full scope of the gospel: it is not just for socially bad people but also for well-informed religious people.  God is not looking for people to have more knowledge about right and wrong; He wants to see what they do with it - does it lead them to repentance?  Does His patience, delaying the judgement that we deserve, impact on our hearts to reveal His loving kindness, not wanting any to perish but all to come to repentance (2 Peter 3:9)?  Does His love stir us to repent?

Religious arrogance is still a problem among believers.  God is patient (the Greek word means ‘slow-angry’), not bringing His wrath upon us earlier, as He calls us to repentance.  But if we think that our Bible knowledge or spiritual experiences make us holy, we will be 'puffed up' (1 Corinthians 8:1, Colossians 2:18).  Such people are spiritually useless and even dangerous.  They avoid the whole point of the gospel – which is to admit sin, believe in Jesus the Saviour, repent and receive His life (www.crosscheck.org.uk).  Today is the day to repent.