Most people think Christianity is a moral improvement project. It's all about the rules.
"Don't drink, cuss, or chew or run with girls who do!"
But to much surprise, Jesus looked at the most moral people on the face of the earth and said, "The prostitutes enter the kingdom of God before you" (Mt 21:31).
Wait. What??
How can a prostitute enter God's kingdom before a priest? Jesus explains in the next verse:
"For John came to show you the way of righteousness, and you did not believe him, but the tax collectors and the prostitutes believed him" (Mt 21:32).
Prostitutes and thieves were entering the kingdom of God before priests because they believed John's message and the priests did not.
OK, so what was John's message?
John summarizes it here: "Behold, the Lamb of God, who takes away the sin of the world" (Jn 1:29).
According to John, the way of righteousness, the way into God's kingdom, is not through a code of ethics, but through a Person.
Christianity says that all of us, priests and prostitutes, have a morality problem; a sin problem (Rm 3:10-12). Since the moment the doctor slapped our rear ends we have all rebelled against God (Ps 51:5). No one merits salvation. No one earns righteousness. No one follows the rules. No one gets to God through good behavior. And therefore all mankind is separated from our holy Creator.
And what is God's response to our rebellion? It's not at all what you would think. Since we couldn't get to God, two thousand years ago in a lowly stable in Bethlehem, God came to us. Jesus, the Lamb of God, came to take away our sin.
"Christ Jesus came into the world to save sinners" (1 Tim 1:15).
Though we rightly deserve punishment for our sin, Jesus, the perfect Son of God, took our punishment for us, in our place, on the cross.
BUT THAT'S NOT ALL!
Jesus not only takes away our unrighteousness, He freely gives us His perfect righteousness!
"For our sake God made him [Jesus] to be sin who knew no sin, so that in him we might become the righteousness of God" (2 Cor 5:21).
Because of Jesus' substitutionary life, death, and resurrection, eternal life now comes to every person the same way: by grace alone, through faith alone, in Christ alone (Eph 2:8-9). God's solution for our inability to follow the rules is not more rules, it's grace! No strings attached. You can't do any good deeds to earn it or bad deeds to lose it. Forgiveness and freedom are yours forever in Christ.
Literally anyone can get in on this.
If you're a prostitute, a thief, a drug addict, a murderer, a liar, a whatever, you can enter God's kingdom before many preachers and Sunday school teachers. How? Not by your good works, but by simply trusting in Jesus' good works (Jn 3:16-17).
This is the gospel. This is Christianity. God doesn't want to make you moral, He wants to make you His. And He does this through the death and resurrection of His Son. Christianity is not a behavioral improvement project, it's a grace project.