Standing on One Foot
A man came to talk with Rabbi Shamai, one of the most famous of all the rabbis, nearly as famous as Rabbi Hillel.
"I would like to convert to Judaism and become a Jew," said the man. "But I don't have much time. I know I have to learn the entire book you call the Torah, but you must teach it to me while I stand on one foot."
The Torah is the most important Jewish book there is, and this crazy man wanted to learn it while standing on one foot? Why, people spent years learning the Torah; it was not something you can learn in five minutes! Rabbi Shamai grew angry with this man, and he pushed the man away using a builder's yardstick he happened to be holding in his hand.
The man hurried away, and found Rabbi Hillel. "I would like to convert to Judaism and become a Jew," said the man. "But I don't have much time. I know I have to learn the entire book you call the Torah, but you must teach it to me while I stand on one foot."
"Certainly," said Rabbi Hillel. "Stand on one foot."
The man balanced on one foot.
"Repeat after me," said Rabbi Hillel. "What is hateful to you, don't do that to someone else."
The man repeated after Rabbi Hillel, "What is hateful to me, I won't do that to someone else."
"That is the whole law," said Rabbi Hillel. "All the rest of the Torah, all the rest of the oral teaching, is there to help explain this simple law. Now, go and learn it so it is a part of you."
Source: Babylonian Talmud, Tractate Sabbath 31a.