Two prominent rabbis, Rav Huna and Rav Chisda, once refused to return the greeting of a colleague named Gniba. Perhaps they considered him insufficiently respectful, or perhaps they were testing him.
Gniba did not walk away offended. He approached them carefully, bowed, and saluted them. Peace upon you, kings. Then he bowed and saluted them again. Peace upon you, kings.
The doubled greeting caught their attention. Why do you call us kings? they asked.
Gniba was ready. He quoted the school of Rabbi Yochanan, which taught that talmidei chachamim — the students of the wise — are properly called kings, because they rule over the inner life through Torah. And he cited the biblical precedent that great blessings are repeated, so the royal greeting should be doubled.
The two rabbis recognized that Gniba had just demonstrated his learning in the very act of greeting them. The formalities of courtesy, in his hands, were a short lecture on kingship and study.
Gaster's Exempla (No. 52, 1924) preserves the scene as a reminder that Torah teaches even through doorways. Every greeting exchanged by scholars is supposed to contain a verse hidden inside the breath.