Our House Is Some Very Fine Boats

When Moses charged us with the Teaching (Torah) as the heritage of the congregation of Jacob, then [God] became Sovereign in Jeshurun (Jeshurun is a poetic name for the People of Israel, meaning "beloved, righteous people")--when the heads of the people assembled, the tribes of Israel together.

In a place where the people were accustomed to perform labor on Passover eve until midday, one may do so on that day. In a place where the people were accustomed not to perform labor, one may not do so. The performance of labor on the eve of Passover is not prohibited by Torah law, but is dependent on local custom. If one travels from a place where people perform labor on Passover eve to a place where people do not perform labor, or from a place where people do not perform labor on Passover eve to a place where people perform labor, the Sages impose upon him the stringencies of both the place from which he left and the stringencies of the place to which he went. In both cases, he may not perform labor. The Sages stated a principle: And a person may not deviate from the local custom, due to potential dispute...

Similarly...(the Mishnah brings more examples of "When in Rome...")

You shall not make gashes in your flesh for the dead, or incise any marks on yourselves: I am Adonai.

"Do not lacerate yourselves" (lo tithgodedu): Do not form opposing factions (agudot, agudot), but all of you consolidate into one bond, as in (Amos 9:6) "and God founded God's bond (agudah) upon the earth."

(11) Variantly, "Do not lacerate yourselves," as others do, as it is written (I Kings 18:29) "and they lacerated themselves, as was their custom."

The Megillah is read on the eleventh, on the twelfth, on the thirteenth, on the fourteenth, or on the fifteenth of the month of Adar, not earlier and not later.

• Cities [kerakin] that have been surrounded by a wall since the days of Joshua, son of Nun, read the Megilla on the fifteenth;
• Villages and large towns that have not been walled since that time read it on the fourteenth.
• However, the Sages instituted that the villages may advance their reading to the day of assembly, i.e., Monday or Thursday, when the rabbinical courts are in session and the Torah is read publicly, and the villagers therefore come to the larger towns.

Abaye said: When we say that the prohibition: “You shall not cut yourselves” applies, we are referring to a case where two courts are located in one city...However, with regard to two courts located in two different cities, we have no problem with it.

Rava said to him: But the dispute between Beit Shammai and Beit Hillel is considered like a case of two courts in one city, as these two schools of thought were found everywhere, not in any specific place. Rather, Rava said: When we say that the prohibition: “You shall not cut yourselves” applies, we are referring to a case where there is a court in one city, a section of which rules in accordance with the statement of Beit Shammai and another section rules in accordance with the statement of Beit Hillel. However, with regard to two courts located in one city, we have no problem with it.

The Talmud cites a number of other relevant cases.....

For three years Beit Shammai (the School of Shmmai) and Beit Hillel (the School of Hillel) disagreed. These said: The Law is as we see it, and those said: The Law is as we see it. A Divine Voice emerged and proclaimed: Both these and those are the words of the living God. However, the Law is in accordance with the opinion of Beit Hillel.

Since both these and those are the words of the living God, why were Beit Hillel privileged to have the law established in accordance with their opinion? The reason is that they were agreeable and forbearing, showing restraint when affronted, and when they taught the halakha they would teach both their own statements and the statements of Beit Shammai. Moreover, when they formulated their teachings and cited a dispute, they prioritized the statements of Beit Shammai to their own statements, in deference to Beit Shammai.

...[This is] to teach you that anyone who humbles themself, the Holy Blessed One exalts God, and anyone who exalts themself, the Holy Blessed One humbles them. Anyone who seeks greatness, greatness flees from them, and, conversely, anyone who flees from greatness, greatness seeks them. And anyone who attempts to force the moment and expends great effort to achieve an objective precisely when he desires to do so, the moment forces them, and they are unsuccessful. And conversely, anyone who is patient and yields to the moment, the moment stands by his side, and he will ultimately be successful.

(1) (Devarim 33:5) "And [God] was Sovereign in Yeshurun": When Israel are of one counsel below, God's great name is exalted above, as it says, "And [God] was Sovereign in Yeshurun" — When? "when the heads of the people gathered." And there is no "gathering" but that of the elders, as it is written (B'midbar 11:16) "Gather unto Me seventy men from the elders of Israel."

(2) (Devarim, Ibid.) "together, the tribes of Israel" — when they constitute one unit, and not when they are divided into many factions, as it is written (Amos 9:6) "Who builds God's heights in the heavens and God's bond on earth endures."

R. Shimon bar Yochai says: This is analogous to one who brought two ships, and tied them to anchors and iron weights, placed them in the heart of the sea, and built upon them stately edifices. So long as the ships are tied together, the edifices endure, but if the ships separate, the stately edifices no longer endure...