In my opinion, the Parable of the Pharisee and the Publican nastily condemns being “sure” that one is Heaven-bound. See Luke 18:9-14.
In that Parable, the Pharisee is a solid citizen. He fasts twice a week. He tithes. He goes to the temple to pray. Tax collectors, on the other hand, were animals. They collected taxes by armed robbery. If you didn’t give in to his gang of thugs asking for everything of value which you had, your sons were murdered, your wife and daughters were raped, and you were savagely beaten, and after looting, your home would be burned. Rome-licensed tax collectors were the Devil’s children, so to speak.
In the Parable, the Tax Collector’s only “redeeming social value” is that he clearly does not believe trhat He is saved, and so he begs for mercy.
The Pharisee, on the other hand, clearly believes that he IS saved.
Jesus declares the Pharisee “unjustified” – still damned – and the tax collector “justified” – saved.
Many see the Pharisee’s words in the Parable – 'O God, I thank you that I am not like the rest of humanity–greedy, dishonest, adulterous–or even like this tax collector. ’ – and conclude that he is damned because of hate.
Not so. One is not damned because he says, “O God, I thank you…that I am not like sexual serial killer Ted Bundy.” The individual whgo says that prayer isn’t even giving credit to himself for being good, but rather to God! A great prayer!
The problem in the Parable is the very pure difference between the Pharisee and the Publican – the Pharisee believes that He has been saved and is definitely Heaven-bound; the Publican clearly does NOT believe that he is Heaven-bound. (Otherwise, why ask for “mercy”?)
In my opinion, the purpose of this Parable is to condemn believing “once saved, always saved.”