The main scripture referred to is Deuteronomy 18:15-20.
When you hire a spokesperson you want them to stay on script and not have their own agenda. In today's reading from Deuteronomy, the Hebrew word translated prophet literally means “spokesperson.” A prophet is called by God to speak for God. “I will put my words in his mouth and he will speak to them all that I command him.”
Of course, this serves as a temptation for people to proclaim themselves to be prophets and say whatever they like. So God says, “But if any prophet presumes to speak anything in my name that I have not authorized him to speak, or speaks in the name of other gods, that prophet must die.” The passage continues beyond our lectionary selection to tell us, “Now if you say to yourselves, 'How can we tell that a message is not from the Lord?'—whenever a prophet speaks in my name and the prediction is not fulfilled, then I have not spoken it; the prophet has presumed to speak it, so you shall not fear him.” (Deuteronomy 18:21-22, NET Bible)
God foresaw the rise of false prophets, people who would pretend to be speaking for God but were just saying things that were self-serving or which served the people who employed them. When Micah condemns the corrupt political and spiritual leaders of Judah he says, “Her leaders take bribes when they declare legal cases, her priests proclaim rulings for profit, and her prophets read omens for pay.” (Micah 3:11) Just this week on Facebook I posted something funny and in the comments was this message. “Actually I was directed to you by my spiritual insight and the universe because it was revealed to me that you need spiritual guidance concerning your life.” The Facebook profile of the person describes them as a “psychic, trauma healer, spiritual coach” and “motivational speaker.” To be fair, they don't say they are a prophet from God. But I am not taking advice from this person or anyone like them.
Jesus also warned us of false prophets. “Then if anyone says to you, 'Look, here is the Christ!' or 'There he is!' do not believe him. For false messiahs and false prophets will appear and perform great signs and wonders to deceive, if possible, even the elect.” (Matthew 24:23-24) He's saying that they can be that persuasive. And a major mark of a destructive cult is that the leader claims to be the Messiah, or Jesus Christ, or God. Jim Jones, David Koresh, Charles Manson, Father Divine, Sun Myung Moon, Yahweh ben Yahweh and many others have declared themselves to be the Messiah. Wikipedia has a whole page listing messiah claimants. Jesus said they can be dismissed as false prophets. If you keep that in mind, you are unlikely to get drawn into a cult.
So how else can we discern which of the many people who claim to be speaking for God are actually false prophets?
As Deuteronomy says, one easy way is when they predict something and it doesn't come true. By this test alone we can eliminate all the people who have predicted the end of the world with a date that is now past. That includes a lot of modern day evangelists, who have been doing this for decades. Charles Taze Russell, Herbert W. Armstrong, Pat Robertson, Louis Farrakhan, Harold Camping, Jerry Falwell, Tim LaHaye, Edgar Cayce, Yisrayl Hawkins, John Hagee and many others have set dates for the end of the world or for Jesus' return which obviously were wrong. Jesus warned us about that. “But as for that day or hour no one knows it—neither the angels in heaven, nor the Son—except the Father.” (Mark 13:32) At least while he was living on earth, even Jesus did not know the date or time! So you can dismiss as a false prophet anyone who thinks they know better than Jesus.
Another way to see if someone is a false prophet is to see if what they say is inconsistent with the canon of scripture. A canon is simply a standard by which things are measured. So 2 Peter says, “Above all, you do well if you recognize this: No prophecy of scripture ever comes from the prophet's personal understanding of things, for no prophecy was ever brought about by the will of a human being; rather, people who were carried along by the Holy Spirit spoke from God.” (2 Peter 2:20-21) How does this help us?
In fandom there is a thing called “head canon.” This is distinguished from canon, which in fandom is what the original show or book says. For instance, in the very first Sherlock Holmes story, Watson is wounded in the shoulder in the first Afghan war. But in other stories his wound is in his leg. Sherlock Holmes fans have come up with a lot of explanations for this discrepancy. Some are clever, some are funny, but none of them are official. The solutions the fans have come up with to explain the problem to their own satisfaction are “head canon,” their own personal way of making sense of things.
Don't misunderstand me but in a way, theological explanations are like head canon. For instance a lot of people think that the reason Jesus died is this: God had to punish someone for our sins but didn't want to punish us, so he punished Jesus instead. Now we are told in the canon of the Bible that Jesus died for our sins (Mark 10:45; Matthew 26:28; John 1:29; Romans 5:8; 1 Corinthians 15:1-4; Galatians 2:20; 1 Peter 2:21-25 and 3:18; 1 John 2:2) But nowhere does it spell out exactly how this worked and nowhere does it say God had to do it because he was required by the Law. So, as a nurse, I like to think of Jesus' death in terms of a transplant from a heart donor. Just as a heart donor must die for you to receive their heart and get a new life, so Jesus' death enables us to receive his eternal life. There are scriptures that suggested that idea to me. (Ezekiel 36:26; Jeremiah 31:33; 2 Corinthians 3:3) That works for me better than the idea that God had to pull some legal trick to get us off from our rightful punishment. But that's my head canon. That Jesus died for us is canon. How you or I explain it is not.
This is not to say theology is worthless. If it helps you understand what the Bible tells us without contradicting what else scripture says, that's good. C.S. Lewis has helped me understand Christianity better. But I don't agree with him on everything. None of us is right about everything. We are all heretics in some area or another. We will only know for sure when we meet God. What's vital is to know the essential truths of the Bible.
And we should be wary of those who add a lot of novelties to the essentials, especially ones that twist the obvious teachings of the Bible. Paul warns his protege Titus, “But avoid foolish controversies, genealogies, quarrels, and fights about the law, because they are useless and empty.” (Titus 3:9) Likewise, he tells Timothy, “For there will be a time when people will not tolerate sound teaching. Instead, following their own desires, they will accumulate teachers for themselves, because they will have an insatiable curiosity to hear new things. And they will turn away from hearing the truth, but on the other hand they will turn aside to myths.” (2 Timothy 4:3-4)
So we can tell if someone is a false prophet when they don't merely share their private interpretation to see if it helps you understand the Bible but instead they substitute it for scripture and that interpretation contradicts the essential teachings of the Bible. John points out such red flags as saying that Jesus is not the Messiah or did not become a flesh and blood human being. (1 John 2:22; 4:3) That's why summaries like the Apostles Creed were compiled by the early church. They tell us in a nutshell what are the basics that we are to believe.
There are also basics of Christian behavior. The Ten Commandments are a good start. And all mainstream religions have some form of the Golden Rule. Jesus put it this way: “Treat others in the same way you would want them to treat you.” (Luke 6:31) Jesus also summarized all the ethical laws in the Bible when he told us to love God with all we are and all we have and to love our neighbor as ourselves. (Matthew 22:37-40)
But Jesus' unique contribution to morality is his extension of the command to love others. He told us we must even love our enemies. (Matthew 5:44; Luke 6:27) No false prophet says that. False prophets are so narcissistic that they cannot tolerate people who question them nor will they usually let people leave their church or cult. Instead they will harass them or even send out followers to harm the defectors. Ervin LeBaron called himself the prophet of his polygamous Mormon fundamentalist group. He sent his followers, including some of his 50 children by his 13 wives, to kill people who left his group or were part of rival groups. It is estimated that he was responsible for between 25 and 50 murders, including those of his own 2 brothers. Jesus never did that. When the disciples reported to him that they tried to stop someone casting out demons in his name, Jesus said, “Do not stop him, for whoever is not against you is for you.” (Luke 9:50) Having different denominations is not a sin. Christians demonizing other Christians is.
Only a false prophet will tell you tell you that murder, adultery, theft, or lying are OK because he says so or that you are to worship something or someone other than God. Again 2 Peter says, “These false teachers will infiltrate your midst with destructive heresies, even to the point of denying the Master who brought them. As a result, they will bring swift destruction on themselves. And many will follow their debauched lifestyles. Because of these false teachers, the way of truth will be slandered. And in their greed they will exploit you with deceptive words.” (2 Peter 2:1-3) A false prophet will use his revelations and teachings to gain wealth or sex or power for himself. Paul said about such people, “If someone spreads false teachings and does not agree with sound words (that is, those of our Lord Jesus Christ) and with the teaching that accords with godliness, he is conceited and understands nothing, but has an unhealthy interest in controversies and verbal disputes. This gives rise to envy, dissension, slanders, evil suspicions, and constant bickering by people corrupted in their minds and deprived of the truth, who suppose godliness is a way of making profit.” (1 Timothy 6:3-5)
Finally, false prophets tend to be more popular than real prophets because they tell people what they want to hear, not what they need to hear. As the fall of Judah to the Babylonians got closer, Jeremiah said, “The Lord God who rules over all says to the people of Jerusalem: 'Do not listen to what those prophets are saying to you. They are filling you with false hopes. They are reporting visions of their own imaginations, not something the Lord has given them to say. They continually say to those who reject what the Lord has said, “Things will go well for you!” They say to those who follow the stubborn inclinations of their own hearts, “Nothing bad will happen to you!”...But if they had stood in my inner circle, they would have proclaimed my message to my people. They would have caused my people to turn from their wicked ways and stop doing the evil things they are doing.” (Jeremiah 23:16-17, 22)
We are seeing this happening today. False prophets are preaching things that not Christian: they are preaching hate; they are preaching that it is OK to be greedy and that God wants us to pursue wealth; they are preaching that we need not do anything to help the poor, the hungry, the sick, the prisoner and the immigrant; they are blessing people's worst attitudes and actions; they are preaching belligerence rather than mercy, retribution rather than forgiveness, the tolerance of injustice and the intolerance of those who disagree with them. And, yes, some who we might otherwise think are Christian are going along with this. They are idolizing those who embody arrogance, lust, laziness, greed, rage, envy and self-indulgence. They are making fun of those who turn the other cheek and calling those who give up their lives for others losers. They exalt the love of power rather than the power of love.
Jesus warned us to “Watch out for false prophets, who come to you in sheep's clothing but inwardly are voracious wolves! You will recognize them by their fruit.” (Matthew 7:15-16) He recognizes them as well. “Not everyone who says to me, 'Lord, Lord,' will enter into the kingdom of heaven—only the one who does the will of my Father in heaven. On that day, many will say to me, 'Lord, Lord, didn't we prophesy in your name, and in your name cast out demons and do many powerful deeds?' Then I will declare to them, 'I never knew you. Go away from me, you lawbreakers!'” (Matthew 7:22-23)
What then is the mark of the true prophet and the true Christian? Hint: you will find it repeated more than 17 times throughout the New Testament. Here it is: on the night before he died for us Jesus said, “I give you a new commandment—to love one another. Just as I have loved you, you also are to love one another. Everyone will know that you are my disciples—if you have love for one another.” (John 13:34-35)