One night, R. Shneur Zalman of Liadi knocked on the Maggid's door. "Who's there?" asked the Maggid.
"It is I," said R. Shneur Zalman.
"Who?" R. Dov Ber repeated.
"It is I," R. Shneur Zalman replied.
"Who?" the Maggid inquired again.
"Shneur Zalman," he answered. With that, he was finally admitted.
At the Maggid's request, the next day R. Shneur Zalman went to a bris milah held in a nearby village. Seeing R. Shneur Zalman's old and tattered clothing, it was assumed that he was a beggar, and he was seated at the end of the table.
When a silver spoon was found missing after the seudah the "beggar" was immediately suspected of theft. Denying the charge, he shouted, "It was not I!" His accusers began to beat him. "It was not I," he repeated.
Eventually, it was discovered that an attendant had taken the spoon, and R. Shneur Zalman was exonerated. When he returned to Mezritch, the Maggid was waiting for him.
"How many times did you have to shout, 'Not I'?" he asked his astounded student.
"Two times you announced to me, 'It is I,' he continued. "There is only One in the universe who may say this. If we are aware of HaShem's presence, how can we, mere mortals, pride ourselves on being 'I'? We must strive for total bittul, self-effacement.
"Twice you called yourself 'I,' so two times you had to announce, 'It is not I.'"