There is a proverb found in the Gemara – מילי בסלע, שתיקותא בתרי – literally; “Words can be worth a coin, but but silence is worth two!”.
It is intended to illustrate the power of being introvert, not speaking when not required.
The Vilna Gaon says that the etymology of the proverb is directly sourced the parsha.
סלע is a unit of currency, but literally translates to “rock”. Eldad and Medad foretold that Moshe was going to die and Yehoshua would bring them into Israel – משה מת, יהושע מכניס – Moshe was to remain in the desert, for the sin of hitting the rock and not speaking to it.
In other words מילי בסלע – if Moshe had spoken to the rock, then שתיקותא בתרי; the two, Eldad and Meidad, would have remained silent – never predicting Moshe’s downfall. Truly, the power of not speaking up.