Not everyone who prophecies and gives a sign that comes to pass is a prophet of God, the reason is because prophets, diviners, psychics, spiritualists etc. look very much alike and has the spiritual ability to reveal hidden things, foretell futures and manifest miracles. As a prophet of God can wear a suit and tie, or white collar to preach in the pulpit, so can a magician transform himself and put on a suite with a bishops collar, change his occultic language to biblical language, and preach and prophesy in Christian’s church services. When Paul the apostle prophesied about the last days events, he compared the false ministers (false prophets) who will arise in the last days to oppose the truth of God with the story of Moses and Jannes and Jambres. Paul stated that the same way Jannes and Jambres withstood Moses in the presence of Pharaoh, would be exactly the same method that the diviners, sorcerers and the psychics who will secretly introduce destructive teachings in the church will resist the truth. Paul called them men of corrupt minds, reprobate concerning the faith (2Timothy3:. Now, Moses and Aaron were true prophets of God, while Jannes and Jambres were the chief magicians of Pharaoh (Exodus7, . Moses and Aaron had the genuine power of God and divine message to call the people of God out of sin and bondage, but Jannes and Jambres apparently had "astonishing" magical powers without an accurate revelation of God, they counterfeited at least three signs that Moses performed in the presence of Pharaoh, King of Egypt. Consider the following scriptures…

Turning a staff into a snake:  So Moses and Aaron went to Pharaoh and did what the LORD had commanded them. Aaron threw down his staff before Pharaoh and his officials and it became a serpent!  Then Pharaoh called in his own wise men and sorcerers, and these Egyptian magicians did the same thing with their magic.  They threw down their staffs, which also became serpents! But then Aaron’s staff swallowed up their staffs (Exodus 7:10-12)

Turning water into blood: So Moses and Aaron did just as the LORD commanded them. As Pharaoh and all of his officials watched, Aaron raised his staff and struck the water of the Nile. Suddenly, the whole river turned to blood!  The fish in the river died, and the water became so foul that the Egyptians couldn’t drink it. There was blood everywhere throughout the land of Egypt.  But again the magicians of Egypt used their magic, and they, too, turned water into blood. So Pharaoh’s heart remained hard. He refused to listen to Moses and Aaron, just as the LORD had predicted (Exodus 7:20-22).

Bringing out Frogs: So Aaron raised his hand over the waters of Egypt, and frogs came up and covered the whole land!  But the magicians were able to do the same thing with their magic. They, too, caused frogs to come up on the land of Egypt (Exodus 8:6-7).

Plague of Gnats: Then the Lord said to Moses, "Say to Aaron, 'Stretch out your rod and strike the dust of the earth, that it may become gnats throughout all the land of Egypt.'" And they did so; Aaron stretched out his hand with his rod, and struck the dust of the earth, and there came gnats on man and beast; all the dust of the earth became gnats throughout all the land of Egypt. The magicians tried by their secret arts to bring forth gnats, but they could not. So there were gnats on man and beast. And the magicians said to Pharaoh, "This is the finger of God." (Exodus 8:16-19).

I hope that you are all aware that Satan can counterfeit God’s manifestation powers; his agents can prophesy and perform miracles, for that reason, it will be difficult to use accurate predictions and miracles to differentiate the true prophets from the sorcerers and the witches and wizards who have transformed themselves as the angels of light to deceive church goers. A discerning of spirits, visions and revelations from the Lord is needed to identify these perpetrators.

Though prophets, psychics and diviners perform similarly in the sight of men, they are totally different in the closet. True prophets walk with the Holy Spirit of God (2peter1:21), while diviners or other fortunetellers walk with familiar spirits “a dark spiritual entity” (1Samuel28:5-14). A prophet approaches God through prayer, by the help of the Holy Spirit he can see what God has in mind concerning people and can also receive the word of the Lord and deliver it accurately to the people without charging any fees (Mathew10:. Contrary to true prophets, sorcerers approach the power of darkness through incantations, they summon a familiar spirit in most cases using a medium such as a crystal ball, tarot cards, monitoring mirrors, ouija boards, beads, dice, cowries, incense, candles and so forth to access information from the spiritual mind of their master “Satan” and to also receive his word and deliver it to the people. As a prophet speaks the accurate mind of God, he speaks to people for their strengthening, encouraging and comfort (1cor14:3).

Diviners always speaks disaster, destruction, discouragement, defeat, confusion and so on to create fear, so out of that fear their subjects will give them money through “donations,”“seeds,” or “gifts”, for instance, when one who is operating with a familiar spirit foretells a good omen concerning you, they will make you pay for it, sometimes by telling you how your enemies want to hijack your blessings, or tells you who wants to kill you just to stop you from receiving the blessings they prophecy to you. Then, for them to pray the danger out of your way, directly or indirectly they will ask you for money. It is difficult for a diviner or spiritualist to give a message that will just encourage and comfort people without inspiring fear, only in rare instances. They only good they can prophesy is the kind of blessing that will add sorrow at the end, or that will take you out off God’s will. Now the reason is because they are not speaking God’s mind, the sorcerers operate in the spiritual realm of darkness, so what they see, hear and predict is the plan and purposes of Satan against humanity. It is significant for people to understand that as God has a good plan for us, 

“For I know the thoughts that I think toward you, saith the LORD, thoughts of peace, and not of evil, to give you an expected end” (Jeremiah29:11).

so does the devil have evil devices towards humanity…

“The enemy said, I will pursue, I will overtake, I will divide the spoil; my lust shall be satisfied upon them; I will draw my sword, my hand shall destroy them” (Exodus15:9).

God’s plan is to give us life, so that we might have it more abundantly, while the devils plan is to steal, kill and destroy (John10:10). And that is why the messengers of darkness always predict calamities, evil, fear, hate, war without solution because that is what their master has in mind concerning us. How can someone who is evil say anything good? For the mouth speaks what the heart is full of.  A good man brings good things out of the good stored up in him, and an evil man brings evil things out of the evil stored up in him(Mathew12:34-36).

God’s messengers speak for edification, exhortation, and comfort because he is speaking from God’s mind. A messenger of God prophesies doom only when he sees evil coming and he will freely speak out, warning and providing solutions according to the will of God to help the people. But as for false prophets, their prophecies are mostly (not always) negative; accidents, death, destruction, hatred bring money before we pray to solve the problem. Another thing is that a true prophet gives a clear prophecy, not in riddle, and when their prophecy comes to pass it will be 100% accurate. Not 95% or even 991/2%, but 100%. The sorcerers always prophesy in riddle, if something close to what they predict happens they will claim that their prediction has come to pass. God controls true prophets so, they never miss. If a prophet misses even one time, that "prophet" is a "false prophet"(Deuteronomy18:20-22).

The challenge we have these days is that those who dont know the person of the holy spirt and his gifts call those who do FAKE.

Mark 9:39
39 But Jesus said, Forbid him not: for there is no man which shall do a miracle in my name, that can lightly speak evil of me. 40 For he that is not against us is on our part,

Finish!

@Joagbaje

It is good to quote a scripture, However, before quoting them, make sure that you have study the verse carefully so that you will not look foolish to those who are seriously studying the scripture and have a spiritual insight in Christ. Now, consider the verse you just quoted…

Mark 9:39 ; 39 But Jesus said, Forbid him not: for there is no man which shall do a miracle in my name, that can lightly speak evil of me. 40 For he that is not against us is on our part. 

Doing something in Jesus name does not suggest doing something and calling his name religiously, it is beyond that bro!  Note; the word that translate name in Greek is “Onoma” which speaks of one’s Character, vision, mission and purposes. So what Jesus Christ is saying in your quoted scripture is that if someone is doing a miracle in full conformity to God’s eternal will and principles, that person is with Christ. In other words, everything that we are doing must be in line with the will of God. please study the following scripture…,

Not everyone who says to Me, ‘Lord, Lord!’ will enter the kingdom of heaven, but 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, drive out demons in Your name, and do many miracles in Your name?’  Then I will announce to them, ‘I never knew you! Depart from Me, you lawbreakers! (Mathew7:21-23)