Deuteronomy 18:20-22 is often read as giving Israel a practical test for prophecy: if a prophet speaks in the name of the LORD and the word does not come to pass, that prophet has spoken presumptuously and must not be feared. Read together with Deuteronomy 13:2-4 (13:1-3 in many English Christian editions), however, the Torah does not make successful prediction a stand-alone credential. Deuteronomy 18 supplies a negative test: if a claimed word in the LORD's name fails, the speaker has spoken presumptuously. Deuteronomy 13 supplies an additional loyalty test: even if a sign or wonder comes to pass, a teacher who uses it to turn Israel toward other gods is to be rejected. Thus, when a prophet offers predictions or signs, accuracy matters, but fulfillment by itself is not sufficient to override Torah covenant fidelity.
This is not an external criticism of the Torah's prophetic standard. It is, in large measure, the way the Torah itself frames the issue, and it is close to the classical Jewish understanding. Classical Jewish interpretation commonly reads the two passages together: signs and predictions can have evidentiary value, but they cannot license idolatry or a permanent revision of Torah. Maimonides' Mishneh Torah, Yesodei haTorah 9-10 is a prominent codified example: chapter 10 discusses testing a prophet by fulfilled predictions, while chapter 9 insists that even a wonder-worker cannot overturn the Torah or command idolatry. The more careful question is what the argument proves, what it does not prove, and how Jewish commentators have qualified it.
The strongest Jewish reading
The traditional Jewish position begins from the unity of Deuteronomy's covenantal theology. Israel is commanded to hear the prophet whom God raises up, but Israel is also commanded never to abandon the exclusive worship of the LORD. Therefore, no wonder-worker, visionary, or predictor can override the foundational covenant.
Deuteronomy 18:22 says that a failed claim in the LORD's name is presumptuous and Israel "shall not be afraid of him." Deuteronomy 13:2-4 then gives the harder case: even if the sign or wonder "comes to pass," Israel must not listen if the message is, "Let us go after other gods."