This Mishnah is more an introduction to the next...one, two...four.
It tells a story of one occasion when quite a few sages went to visit a sick colleague. Finding that there were quite a few sages present, they sat down to an impromptu Torah-gathering and started discussing laws that they had been deliberating.
Scholars from the House of Shammai, which were normally in the minority, found that at this particular gathering they formed the majority - and took advantage of that to establish several laws according to their opinion. Those laws follow in the next four Mishnayos (plural of Mishnah), as I mentioned above.
Continue for a pair of side points - well, more detailed explanations, really.
(Side point - The House of Hillel and the House of Shammai:
Hillel and Shammai were colleagues and co-leaders of their generation. Each had a very different nature; while both were incredibly studious, Shammai's innate nature was strict/diligent and Hillel's was more open/accepting.
Due to their natures, Shammai attracted only the sharpest and brightest scholars among the nation, while Hillel attracted any who truly had a desire to learn. Hillel accepted anyone who truly desired to learn, with there being a couple of well-known and quoted stories in the Talmud of prospective converts who came to each with...odd...prerequisites to their conversion.
The scholars of the House of Shammai were acknowledged as the smarter, but the scholars of the House of Hillel were more numerous. So to this day, the vast majority of laws follow the House of Hillel's opinion.)
(Side point - Establishing law in Judaism:
In short, it's done based on the majority vote of a court of sages. As each sage may understand the laws and their reasoning/sources different from each other, much discussion takes place before a majority consensus is reached. But once the law has been decided, it's done. Courts of lesser standing cannot dispute or revoke that law (or judgement, if it was a specific ruling); only the original court or one considered greater can change it.)
Put those together, you'll understand how the House of Shammai slipped those laws under the rug. They weren't revoked, either; they stand.
Posted by adam at May 12, 2006 08:05 AM