Isaac Horowitz lived in New York and his son was away at school overseas and he wanted to send him a chumash so his son could review the weekly Torah portion. After wrapping the chumash in plenty of bubble wrap and placing it carefully inside a cardboard box, Isaac seals the box, writes his son's name and address on the label, and then takes it to the local Post Office.
When he gets to the front of the line, Isaac hands the box to the clerk behind the counter.
"Is there anything breakable inside the box, sir?" asks the clerk.
Without thinking, Isaac replies, "Only the Ten Commandments."