Genesis Rabbah 24 (XXIV:vii, 3.A.-3.B.; Neusner)

Ben Azzai said, "‘This is the book of the generations of man’ represents the encompassing principle of the Torah [since it shows that all of humanity comes from a single progenitor]."

R. Aqiba said, "‘You shall love your neighbor as yourself’ (Gen. 19.18) is the encompassing principle of the Torah. [It goes further than merely indicating that everyone is related.] For you should not say, ‘Since I have been humiliated, let my fellow be humiliated. [Since a person does not want to be humiliated, he should not humiliate his fellow, even if he has been so treated.]’"