Yevamot

R. Johanan, however, said: They certainly acted [in accordance with their views]. Herein they  differ on the same point as do Rab and Samuel. For Rab maintains that Beth Shammai did not act in accordance with their views, while Samuel maintains that they certainly did act [in accordance with their views]. When?  If it be suggested, prior to the decision of the heavenly voice,  then what reason has he who maintains that they did not act [in accordance with their own view]? If, however, after the decision of the heavenly voice, what reason has he who maintains that they did act [in accordance with their views]? — If you wish I could say, prior to the decision of the heavenly voice; and if you prefer I could say, after the heavenly voice. 'If you wish I could say, prior to the heavenly voice', when, for instance, Beth Hillel were in the majority: One maintains  that they  did not act [according to their view] for the obvious reason that Beth Hillel were in the majority; while the other maintains  that they did act [according to their view, because] a majority is to be followed only where both sides are equally matched;  in this case, however, Beth Shammai were keener of intellect. 'And if you prefer I could say, after the heavenly voice'; one maintains that they  did not act [according to their view] for the obvious reason that the heavenly voice had already gone forth;  while the other who maintains that they did act [according to their view] is [of the same opinion as] R. Joshua who declared that no regard need be paid to a heavenly voice. Now as to the other who 'maintains that they did act [according to their views]'  — should not the warning, 'Lo tithgodedu, you shall not form separate sects'  be applied? — Abaye replied: The warning against opposing sects is only applicable to such a case as that of two courts of law in the same town, one of whom rules in accordance with the views of Beth Shammai while the other rules in accordance with the views of Beth Hillel. In the case, however, of two courts of law in two different towns [the difference in practice] does not matter. Said Raba to him: Surely the case of Beth Shammai and Beth Hillel is like that of two courts of law in the same town! The fact, however, is, said Raba, that the warning against opposing sects is only applicable to such a case as that of one court of law in the same town, half of which rule in accordance with the views of Beth Shammai while the other half rule in accordance with the views of Beth Hillel. In the case, however, of two courts of law in the same town [the difference in practice] does not matter. Come and hear: In the place of R. Eliezer, wood was cut on the Sabbath wherewith to produce charcoal on which to forge the iron.  In the place of R. Jose the Galilean the flesh of fowl was eaten with milk.  In the place of R. Eliezer only  but not in the place of R. Akiba; for we learnt: R. Akiba laid it down as a general rule that any labour which may be performed on the Sabbath Eve  does not supersede the Sabbath!  — What an objection is this! The case, surely, is different [when the varied practices are respectively confined to] different localities. What then did he who raised this question imagine?  — It might have been assumed that owing to the great restrictions of the Sabbath [different localities are regarded] as one place, hence it was necessary to teach us [that the law was not so]. Come and hear: R. Abbahu, whenever he happened to be in the place of R. Joshua b. Levi, carried  a candle,  but when he happened to be in the place of R. Johanan  he did not carry a candle!  — What question is this! Has it not been said that the case is different [when the varied practices are respectively confined to] varied localities? — This is the question:  How could R. Abbahu act in one place in one way and in another place in another way?  — R. Abbahu is of the same opinion as R. Joshua b. Levi,  but when he happened to be in R. Johanan's place he did not move a candle out of respect for R. Johanan. But his attendant,  surely was also there!  — He gave his attendant the necessary instructions. Come and hear: THOUGH THESE FORBADE WHAT THE OTHERS PERMITTED … BETH SHAMMAI, NEVERTHELESS, DID NOT REFRAIN FROM MARRYING WOMEN FROM THE FAMILIES OF BETH HILLEL, NOR DID BETH HILLEL [REFRAIN FROM MARRYING WOMEN] FROM THE FAMILIES OF BETH SHAMMAI. Now, if it be said that they  did not act [in accordance with their own view] one can well understand why THEY DID NOT REFRAIN [from intermarrying with one another].  If, however, it be said that they  did act [in accordance with their own view], why did they not refrain? That Beth Shammai did not refrain from marrying women from the families of Beth Hillel may well be justified because such  are the children of persons guilty only of the infringement of a negative precept;  but why did not Beth Hillel refrain from [marrying women from the families of] Beth Shammai? Such,  surely, being children of persons who are guilty of an offence involving kareth, are bastards!  And if it be suggested that Beth Hillel are of the opinion that the descendant of those who are guilty of an offence involving kareth is not a bastard,  surely, [it may be retorted], R. Eleazar said: Although Beth Shammai and Beth Hillel are in disagreement on the questions of rivals, they concede that a bastard is only he who is descended from a marriage which is forbidden as incest and punishable with kareth! Does not this then conclusively prove that they  did not act [in accordance with their own view]? — No; they  acted, indeed, [in accordance with their own view], but they  informed them  [of the existence of any such cases] and they  kept away. This  may also be proved by logical inference; for in the final clause it was stated. [SIMILARLY IN RESPECT OF] ALL [THE QUESTIONS OF RITUAL] CLEANNESS AND UNCLEANNESS, WHICH THESE DECLARED CLEAN WHERE THE OTHERS DECLARED UNCLEAN, NEITHER OF THEM ABSTAINED FROM USING THE UTENSILS OF THE OTHERS FOR THE PREPARATION OF FOOD THAT WAS RITUALLY CLEAN.