On today’s daf the Gemara relates a series of famous stories of non-Jews who come before the Sages Shammai and Hillel asking to convert, only to find that Shammai is unwelcoming, and Hillel encouraging. As an example, one of the stories teaches:
There was another incident involving one gentile who came before Shammai and said to Shammai: Convert me on condition that you teach me the entire Torah while I am standing on one foot. Shammai pushed him away with the builder’s cubit in his hand. This was a common measuring stick and Shammai was a builder by trade. The same gentile came before Hillel. He converted him and said to him: That which is hateful to you do not do to another; that is the entire Torah, and the rest is its interpretation. Go study.
The Maharsha explains that apparently, the intention of the gentile was to ask the Sage for a single fundamental principle, “one foot,” upon which all of Judaism is based. Indeed, just as Hillel based the Torah upon this single principle, so too Rabbi Akiva and ben Azzai later attempted to formulate the same concept in different, broader terms.
The phrase “That which is hateful to you do not do to another” appears in the Aramaic translation, Targum Yonatan, of the Torah verse: “And you shall love your neighbor as yourself” (Vayikra 19:18). It is not a precise translation; rather, it is a limited interpretation. It does not express the positive mitzva to love another, but the prohibition, proscribing actions harmful to others. Apparently, Hillel sought to express through this principle that at the basis of the Torah are those mitzvot, which are fundamental principles that may be universally applied.
It should be noted that in practice, people like the ones Hillel converted are not accepted as converts because the halakha insists that a convert accept upon himself the entire Torah without intention to accrue personal benefit. However, Hillel apparently relied on the fact that these converts could eventually accept Judaism in its entirety at a later time.