It happened that a certain heathen came before Shammai and said to him, "Make me a proselyte, on condition that you teach me the whole Torah while I s

tand on one foot." Thereupon he repulsed him with a builder's cubit which was in his hand. When he went before Hillel, he said to him, "What is hateful to you, do not to your neighbor: that is the whole Torah, while the rest is the commentary thereof; go and learn it."
(Talmud, Tractate Shabbah 31a)