Evangelical Christians agree that the biblical canon has been established. Anyone who claims to have a prophetic word must demonstrate its validity from Scripture. According to 1 Corinthians 14, any supposedly prophetic statement must pass two tests. First, verse 29 states that after two or three speak a prophetic message, the others are to “judge.” In other words, the prophetic message must not disagree with the knowledge of God’s Word and of truth held by other members of the assembly. Second, verses 37 and 38 demonstrate that just as the apostle Paul submitted his words to the examination of the Corinthians upon the basis of their knowledge of the Word of God, any prophecy that is given must be judged by the standard of the truth already known to the church of Christ. In other words, no completely new truth will be revealed, but rather the prophet will expound and explain truths already accepted and recognized by God’s people. Any “prophecy” that conflicts with Scripture is assumed to be false.
Evangelicals also know how seriously the Old Testament viewed false prophecy. It provided two tests to determine whether prophets were true or false. Deuteronomy 13:1-3 states the first.  If a prophet calls upon the people to “go after other gods,” he is to be considered false, even if his prophecy is fulfilled.
If a prophet or a dreamer of dreams arises among you and gives you a sign or a wonder, and the sign or the wonder comes true, concerning which he spoke to you, saying, “Let us go after other gods (whom you have not known) and let us serve them,” you shall not listen to the words of that prophet or that dreamer of dreams; for the Lord your God is testing you to find out if you love the Lord your God with all your heart and with all your soul (nasb).
The second test has to do with the prophet’s accuracy:
When a prophet speaks in the name of the Lord, if the thing does not come about or come true, that is the thing which the Lord has not spoken. The prophet has spoken presumptuously; you shall not be afraid of him (18:22).
Deuteronomy 13:5 and Deuteronomy 18:20 explicitly state the punishment for false prophets: They shall be put to death.
Yet although many evangelicals are wary of anyone claiming to be a prophet, some are dangerously naive about prophetic speculation. Many of those who would never claim to be a “prophet” (See the ATQ article, Do the Same Kinds of Prophets Exist Today as in Biblical Times?) don’t hesitate to claim authoritative insight into the meaning of prophecy. While they would never say, “Thus saith the Lord,” they seem to imply that they know what God was saying through the prophet.
The purpose of all prophecy—including prophecy about future events—is to encourage us to examine ourselves, repent, and turn from our evil ways. Sometimes prophecy describes a future event to give hope, sometimes it warns of judgment, but in every case the goal of prophecy is spiritual renewal.  Prophetic speculation, on the other hand, is mostly concerned with linking contemporary events to biblical prophecy.
To say this contemporary event is a fulfillment of that prophecy is to claim a kind of prophetic authority. It is a form of “speaking in the name of the Lord” (Deuteronomy 18:22), and just as in the case of false prophecy, it has serious consequences. Scripture and history show that prophecy pertaining to future events is ambiguous before the events occur. (See the ATQ article Can We Know if Current Events are Fulfillment of Prophecy?) Previous historical attempts to predict future events on the basis of biblical prophecy have been disastrous. (See the ATQ article How often in the History of the Church have People Mistakenly Believed They Were Acting in Fulfillment, or Observing the Fulfillment of Prophecy?)
Believing we belong to a small group that understands how prophetic events are unfolding can lead to unintended results, including pride, isolation, and diminishing concern with truth and reality. It can transform one’s interpretation of prophecy into an idol, a false god. If enough people are influenced, false speculation can lead to its own “fulfillment”—the satanic opposite of legitimate prophecy–accompanied by self-righteousness, fanaticism, and violence.
This is what happened in Israel in 70 and 135 AD. False prophecy and false prophetic speculation about Messiah led to the destruction of Jerusalem by Roman armies. The fact that many Jews were convinced that Messiah would free Israel from the Roman yoke made them vulnerable to the influence of fanatics. (See the ATQ article How often in the History of the Church have People Mistakenly Believed They Were Acting in Fulfillment, or Observing the Fulfillment of Prophecy?) The same tendency can be seen in those today whose interpretation of prophecy allows them to ignore basic issues of justice and morality while calling for unqualified support for Israel in the modern Middle East, military action, the initiation of new wars, and even the use of nuclear weapons.
It is no wonder that the New Testament discourages speculation about when Jesus Christ will return and specifically states that He will return at a time no one expects (Matthew 24:36-50;25:13; Acts 1:7; 1 Thessalonians 5:2; 2 Peter 3:10).
Jesus Christ and other inspired writers not only warn us against speculation concerning the hour of His return, but they imply such speculation prevents serious preparation for His return (Matthew 24:43-44; 1 Thessalonians 5:1-6; Revelation 3:3).
Whether it manifests itself in apathy or fanatic violence, false prophecy and false speculation about prophecy is dangerous. Those of us who get caught up in the destructive practice of prophetic speculation not only lend support to the principalities and powers of evil, but also sow seeds of disillusionment and rebellion against the gospel and biblical revelation. Mark 9:42declares: “Whoever causes one of these little ones who believe in Me to stumble, it would be better for him if a heavy millstone were hung around his neck, and he were thrown into the sea” (nkjv).