Once Mar Zutra travelled to a certain city with many of his students. A wealthy Jew who lived in that city invited them all to stay at his house as guests for Shabbat.

The host treated them with the greatest respect, serving them wonderful meals, and honoring the Torah which they discussed.

Among the treasured possessions of the host was a beautiful silver goblet of rare workmanship, which he used for kiddush and havdala -- the service after Shabbat, separating Shabbat from the rest of the week. After Shabbat, as the servants were cleaning up and putting everything away, a cry suddenly arose in the household. The goblet was missing. Everyone looked high and low for it, but to no avail. It had vanished.

Everyone was bewildered. Mar Zutra and his students also helped in the search. But the goblet was not to be found.

The host was very upset. Reluctantly he said, "I am afraid that our precious goblet has been stolen!"

Mar Zutra was deeply troubled. Was it possible that one of his students had done such a terrible thing?

The students looked at one another with serious faces. They hoped that the thief would be discovered quickly. They did not want to be suspected of stealing. Everyone went to sleep with a troubled heart.

The next morning the students woke up and prepared for prayers. Immediately upon arising, each one carefully did the mitzva of washing his hands. Mar Zutra watched them with approval.

Then he noticed that one of the students wiped his hands on another student's cloak. Mar Zutra called the student aside, and said to him sternly, "Admit that you are the thief!"

"Rebbe, how can you say that?" the student protested.

"I saw you wiping your hands on another student's garment!" Mar Zutra said. "If you don't care about his garment, why should you care not to steal as well?"

"But I couldn't find my towel, and the garment will soon be dry. I didn't really damage it."

"Nonsense!" Mar Zutra said. "If you couldn't find your own towel, why didn't you wipe your hands on your own shirt instead? You pretend to fear G-d when you wash your hands, but you really are a thief! Your own actions betray you!"

The student's belongings were searched, and the goblet was discovered. Since he had been careless in one little thing, Mar Zutra had rightly understood that the student was a thief.