Three Thousand Forgotten Halachos

During the days of mourning for Moshe, three thousand halachos were forgotten. The people said to Pinchas, "Ask Hashem." He answered them, "It is not in the heavens" (Devarim 30:12).

They then said to Elazar, "Ask Hashem." He answered, "These are the commandments" (Vayikra 27:34), teaching that a prophet may not use prophecy to reveal laws.