How do we know self-righteousness keeps people from heaven?

Self-righteousness is a significant barrier to entering heaven as it leads individuals to believe they can achieve righteousness through their own efforts. As stated in the sermon, it is not one's sin that keeps them out of heaven, but rather the belief that they are deserving of salvation based on their deeds. Jesus illustrates this in the parable of the Pharisee and the publican, where the self-righteous Pharisee could not enter due to his reliance on his works. This highlights that true entrance into the kingdom requires a recognition of one's own unworthiness and a plea for Christ's mercy, as illustrated in Luke 13:24.