Rabbi Yochanan ben Elazar owned a tree whose branches had grown out over his neighbor's field. The neighbor had never complained — rabbinic scholars were generally given deference — but the tree was there, and its shade fell on someone else's crops.
One day a man came to Rabbi Yochanan with a legal complaint. His neighbor's tree was overhanging his field, and he wanted a ruling that would force the neighbor to cut back the branches.
The Ruling Postponed by a Day
Rabbi Yochanan listened to the case. Then he said, "Come back tomorrow for my judgment."
That night he went home, picked up an axe, and cut down his own overhanging tree.
The next morning, when the plaintiff returned, Rabbi Yochanan rendered his ruling: the defendant must cut down his overhanging tree. He then turned to the man and said, "I have cut down mine. Now you go and do likewise to yours."
The Principle Behind the Axe
The Gaster exempla, drawing from the Mishnah Bava Batra, preserves this story as a case study in the principle of naaseh ki-dvarav — "his deeds matched his words." A judge may not issue a ruling that he himself does not obey first. The moral authority to bind another person flows from having bound yourself.
Rabbi Yochanan did not wait to be asked about his own tree. He did not rationalize that his case was different. He made sure, before he opened his mouth in judgment, that no one could point to his field and ask why the standard that applied to his neighbor did not apply to him.
The axe fell on his own branches first. Only then could it speak.