Harden not your hearts the apostle exhorts us probably from prison where he wrote most od these letters from. But rather believe as did Paul. Before Jesus appeared unto him on the road to Damascus, Paul was still zealous in his religous beliefs. Above his fellow scholars, scribes and pharicees. And God took notice for there was new wine to be put into old bottles and Paul had to be "broken" first. The bible is full, pregnant with these lessons for all to partake from for God wants us to have the knowledge given to his Son so that we can be like him, for the deciple cannot be greater than his Master.