Jesus contrasted religious and righteous prayer in a parable in Luke 18:9-14.  When his disciples were curious why He spoke to people in parables (Matthew 13:10), Jesus answered in two different ways, first (Matthew 13:11, 12 NET):

You have been given the opportunity to know the secrets of the kingdom of heaven, but they have not.  For whoever has will be given more, and will have an abundance.  But whoever does not have, even what he has will be taken from him.

Usually, Jesus’ disciples asked for, and received, further explanation what the parables meant.  Jesus continued (Matthew 13:13-15 NET):

For this reason I speak to them in parables (παραβολαῖς, a form of παραβολή): Although they see they do not see, and although they hear they do not hear nor do they understand.  And concerning¹ them the prophecy of Isaiah² is fulfilled that says: ‘You will listen carefully yet will never understand, you will look closely yet will never comprehend.  For the heart of this people has become dull; they are hard of hearing, and they have shut their eyes, so that they would not see with their eyes and hear with their ears and understand with their hearts and turn, and I would heal³ them.’

So a parable, without an explanation, was deliberately designed to be cryptic, its actual meaning hidden beneath something obvious—Although they see they do not see, and although they hear they do not hear—but misleading—nor do they understand.  Here is the parable (Luke 18:9-14 NET):

Jesus also⁴ told this parable to some who were confident (πεποιθότας, a form of πείθω) that they were righteous (δίκαιοι, a form of δίκαιος) and looked down on everyone else.  “Two men went up to the temple to pray, one a Pharisee and the other a tax collector.  The Pharisee stood and prayed about himself like this: ‘God, I thank you that I am not like other people: extortionists, unrighteous (ἄδικοι, a form of ἄδικος) people, adulterers (μοιχοί, a form of μοιχός) – or even like this tax collector.  I fast twice a week; I give a tenth of everything I get.’  The tax collector, however,⁵ stood far off and would not even look up to heaven, but beat⁶ his breast and said, ‘God, be merciful to me, sinner that I am!’  I tell you that this man went down to his home justified (δεδικαιωμένος, a form of δικαιόω) rather than⁷ the Pharisee.⁸  For everyone who exalts (ὑψῶν, a form of ὑψόω) himself will be humbled (ταπεινωθήσεται, a form of ταπεινόω), but he who humbles (ταπεινῶν, another form of ταπεινόω) himself will be exalted (ὑψωθήσεται, another form of ὑψόω).”

As I understand it some Pharisees looked down on tax collectors because the latter supported (and profited from supporting) Gentile sinners, the Roman government, by collecting (and sometimes, extorting) money from the god-fearing of Israel.  Many Pharisees viewed Roman rule as illegitimate and believed that Messiah was coming soon to set things right.

What I now call my religious mind helped me misunderstand this parable for years.    Obviously, I hope what I think now shares in the mind of Christ,⁹ but had you asked me then I probably would have assured you that what I now call my religious mind was the mind of Christ.  Bible study can be like that.  At the end of the book of Judges—In those days Israel had no king; Each man did what he considered to be right¹⁰—I assumed that God wanted Israel to have a king and the events described in the book of Judges were the reasons why.  When I read 1 Samuel 8 I had to rethink that assumption.  I’ll try to explain the difference between my religious mind and what I now think.

What shall we say then?  Is there injustice (ἀδικία)¹¹ with God?  Absolutely not!  For he says to Moses:¹² “I will have mercy on whom I have mercy, and I will have compassion on whom I have compassion.”  So then, it does not depend on human desire or exertion, but on God who shows mercy.¹³

Addendum: September 28, 2018
Tables comparing Mathew 13:14, 15; Luke 18:9; 18:13, 14 and Romans 9:15, 16 in the NET and KJV follow.