False prophets by their lies they make the hearts of many believers sad.
Here is how;
First, this is what Jesus said he came to do
 Suppose ye that I am come to give peace on earth? I tell you, Nay; but rather division:  For from henceforth there shall be five in one house divided, three against two, and two against three.  The father shall be divided against the son, and the son against the father; the mother against the daughter, and the daughter against the mother; the mother in law against her daughter in law, and the daughter in law against her mother in law.
“And Jesus said, For judgment I am come into this world, that they which see not might see; and that they which see might be made blind.” John 9:39
“He that loveth his life shall lose it; and he that hateth his life in this world shall keep it unto life eternal.” John 12:25
This is what the apostles taught
“Therefore I take pleasure in infirmities, in reproaches, in necessities, in persecutions, in distresses for Christ’s sake: for when I am weak, then am I strong.” 2 Corinthians 12:10
“Teaching us that, denying ungodliness and worldly lusts, we should live soberly, righteously, and godly, in this present world;  Looking for that blessed hope, and the glorious appearing of the great God and our Saviour Jesus Christ.” Titus 2:12-13
“Yea, and all that will live godly in Christ Jesus shall suffer persecution.” 2 Timothy 3:12
 And account that the longsuffering of our Lord is salvation; even as our beloved brother Paul also according to the wisdom given unto him hath written unto you;  As also in all his epistles, speaking in them of these things; in which are some things hard to be understood, which they that are unlearned and unstable wrest, as they do also the other scriptures, unto their own destruction.  Ye therefore, beloved, seeing ye know these things before, beware lest ye also, being led away with the error of the wicked, fall from your own stedfastness.” 2 Peter 3:15-17
This is what false prophets are teaching; peace and prosperity, and all such lies.
“For there are many unruly and vain talkers and deceivers, specially they of the circumcision: Whose mouths must be stopped, who subvert whole houses, teaching things which they ought not, for filthy lucre’s sake.” Titus 1:10-11
What things do they teach?
The first ever false prophet to preach prosperity gospel to mankind, do you know who that is? The serpent in Genesis 3, and all the false prophets “…is after the working of Satan with all power and signs and lying wonders.” 2 Thessalonians 2:9
The serpent was more subtil than any beast of the field which the Lord God had made. Does this remind you of any such subtil creatures of our time?
False prophets of course,
“…beware lest ye also, being led away with the error of the wicked, fall from your own stedfastness...”
Isaiah 56:11 says,
“Yea, they are greedy dogs which can never have enough, and they are shepherds that cannot understand: they all look to their own way, every one for his gain, from his quarter.”
If your prophet is genuine why is he preaching another gospel which is different from that of Christ and his apostles?
Ezekiel 13:22 says, “Your lies have discouraged the righteous when I didn’t want it so. And you have encouraged the wicked by promising life, though they continue in their sins.”
Only the lost are they who are encouraged by their false promises.
Therefore thus saith the Lord God ; Because ye have spoken vanity, and seen lies, therefore, behold, I am against you, saith the Lord God .  And mine hand shall be upon the prophets that see vanity, and that divine lies: they shall not be in the assembly of my people, neither shall they be written in the writing of the house of Israel, neither shall they enter into the land of Israel; and ye shall know that I am the Lord God .  Because, even because they have seduced my people, saying, Peace; and there was no peace….” Ezekiel 13:8-10 KJV