דברים, פרק י״ח, פסוק כ״ב

A practical test is established to identify a false prophet and ensure he is judged without hesitation. For a prophet to be held liable, he must speak explicitly in the name of God; casual or general predictions do not trigger these severe consequences [נחל קדומים]. The ultimate proof of deception is simply that the predicted event fails to materialize. However, this presents a significant theological challenge. Prophecies of doom can be averted if the people repent, just as promises of good can be withdrawn if the people sin. How, then, can the failure of a prediction serve as definitive proof of a prophet's falsehood?

The primary approach among commentators is that this test applies specifically to neutral prophecies that are entirely independent of human merit or guilt, such as the prediction of a miraculous sign [רלב"ג, בכור שור]. Alternatively, the test applies to positive prophecies delivered as absolute, finalized decrees, which cannot be revoked by God. If such an absolute promise fails, the prophet is undoubtedly an impostor [גור אריה, מזרחי]. Furthermore, even if the vast majority of a prediction comes true, the failure of a single, minor detail is enough to prove that the message did not originate from God [העמק דבר].

God governs the world through two distinct modes, both of which are addressed in the criteria for testing a prophet. A prediction might involve an open, supernatural miracle performed directly by God, or it might involve natural events brought about through human agents. Whether the prophecy relies on the miraculous or the mundane, its failure exposes the prophet as a fraud [הכתב והקבלה, אדרת אליהו]. This absolute failure stands in stark contrast to a prophet who incites the masses toward idolatry. In that scenario, a predicted sign might actually come true as a divine test to see if the people will remain faithful, whereas the standard false prophet's sign will never materialize at all [חזקוני].

The criteria for false prophecy extend beyond predicting the future. If a prophet issues a practical directive in the name of God intended to permanently uproot a Torah law, he must be ignored. The only exception is a universally recognized, righteous prophet who issues a temporary, emergency ruling to address an urgent crisis, much like Elijah offering a sacrifice outside the Temple to combat idolatry [רש"י, ספורנו, בכור שור, דברי דוד]. In all cases of false prophecy, the deception stems from malice and a deliberate desire to sin, rather than an innocent mistake or a confusing dream [אדרת אליהו, ביאור שטיינזלץ].

Finally, the biblical judges are commanded to prosecute the false prophet without hesitation or fear. This directive addresses several natural anxieties. A false prophet often presents himself as a deeply holy and prominent figure, leading judges to fear his spiritual power or a potential curse [העמק דבר, מזרחי, רלב"ג]. Additionally, the impostor might preach the observance of genuine commandments alongside his falsehoods, creating confusion and hesitation in the courtroom [תורה תמימה]. Judges might also carry a profound fear of making a judicial error and accidentally executing a true prophet [גור אריה]. Therefore, they are firmly commanded to cast aside their fears, whether of the man himself or of heavenly retribution, ensuring the land is cleansed of false beliefs and innocent blood [רש"י, אבן עזרא, שפתי חכמים].