עקידת יצחק
Akeidat Yitzchak 96:1
Q — How is Israel to know a false prophet from a true one? If the test is whether his words come true, what of a prophet who predicts good that fails, or evil that God mercifully averts? Why give a sign at all?
A — The Torah provides a clear criterion — true nevuah is recognized by the fulfillment of its words — while distinguishing the cases: a prophecy of good God will not retract, so its failure exposes a false prophet, whereas a decree of evil may be annulled through teshuvah without impugning the prophet. The sign anchors prophecy in verifiable reality, protecting Israel from imposters, yet it is calibrated to the asymmetry of divine promise and threat, so that mercy's reversal of a harsh decree is never mistaken for falsehood.
יבטל דעת האומר שמדה טובה היוצאת מהקב"ה על פי נביא אינה חוזרת: נביא אקים להם. וכי תאמר בלבבך איכה נדע וגו'.