Journey

Musa is about to embark on a long journey & decides that his wife should wear steel underwear .
He locks it & gives the key to his friend, Ben, saying "If I don't come back in 10 years time, pls unlock it & set her free". Musa sets out on his journey & half an hour later sees a cloud of dust behind him. He waits & sees Ben running after him."What's wrong?" he asks. Panting, Ben says "You gave me the wrong key!!