Hillel's Golden Rule — The Essence of Torah
Hillel's formulation of the Golden Rule — 'What is hateful to you, do not do to your neighbor — that is the whole Torah; the rest is commentary' — distills all of Jewish ethics into a single principle.
When a gentile came to Hillel and asked to be taught the entire Torah while standing on one foot, Hillel responded: 'What is hateful to you, do not do to your fellow. That is the whole Torah; the rest is commentary. Go and learn.' (Babylonian Talmud, Shabbat 31a). This formulation — expressed in the negative ('do not do') rather than the positive ('do unto others') — is considered by many commentators to be more philosophically careful than the positive Golden Rule, since we cannot always know what others want but can more reliably identify what is harmful. Hillel's teaching does not reduce the Torah to a single rule and abandon the rest — it says 'the rest is commentary' meaning that all 613 mitzvot are the elaboration and application of this core principle in all the specific situations of human life. Rabbi Jonathan Sacks called this the 'minimum definition of morality' — the floor below which no civilized behavior can fall.
What is hateful to you, do not do to your neighbor. That is the whole Torah; the rest is commentary. Go and learn.
Ethicist R.M. Hare's 'universalizability' principle — that moral rules must be applicable to all relevantly similar cases without exception — is the philosophical articulation of what Hillel's Golden Rule practices: genuine moral reasoning requires the ability to see oneself in the position of the other.
Talmud Bavli