Talmud for Yevamot 27:20

²⁴³Tosephta 1:10, Babli 14b.“Even though the House of Shammai and the House of Hillel disagreed about co-wives²⁴⁴Discussed in the Mishnah here., and sisters²⁴⁵Mishnah 3:1, about two sisters married to two brothers who both die childless at the same time., and an old bill of divorce²⁴⁶The House of Hillel hold that if a man divorces his wife and then spends time with her under circumstances that permit sexual relations, the bill of divorce is invalidated and the woman needs a new one to marry again. The House of Shammai disagree and hold that if they sleep with one another they do it in intended promiscuity. What the Tosephta calls “an old bill of divorce”, Mishnah Giṭṭin 8:8 calls “he who divorces his wife and spends the night with her in a hostelry.”, and a woman doubtfully married²⁴⁷There are several cases of disagreement about the status of a woman in the Mishnah, and Rashi, R. Ḥananel, and S. Lieberman all have their own preferences. Probably this refers to all instances., and one who gives qiddushin in the value of a peruṭa,²⁴⁸Mishnah Qiddušin 1:1. In qiddushin, the man has to give the woman something of value to make the act legally binding. The value according to the House of Hillel must be at least a peruṭah, the smallest copper coin in Hasmonean times, long out of circulation in Mishnaic times. The House of Shammai require a denar, the larger Roman silver coin in the early Empire. i. e., he who divorces his wife and spends the night with her in a hostelry, and that a woman receives qiddushin for at least a denar or the value of a denar, the House of Shammai did not refrain from marrying women from the House of Hillel or the House of Hillel from the House of Shammai but they behave truthfully and in peace, as it is said²⁴⁹Zach. 8:19.: ‘Love truth and peace.’ ” Bastardy is between them and you say so? How is that? If a first man gives her qiddushin for a peruṭa and a second for a denar, in the opinion of the House of Shammai she is betrothed to the second and the child of the first is a bastard. In the opinion of the House of Hillel she is betrothed to the first and the child of the second is a bastard²⁵⁰In the Babli, the discussion is about the more realistic case of the daughter’s co-wife, where the child is a bastard for the House of Hillel in a levirate following the House of Shammai but only damaged (unfit for a Cohen) for the House of Shammai if married outside following the House of Hillel.. Rebbi Jacob bar Aḥa in the name of Rebbi Joḥanan: The House of Shammai concede to the House of Hillel as a restriction²⁵¹They would never permit a new marriage if an existing one is valid for the House of Hillel. There remains the difference that, if it happened, the qiddushin of the second are invalid, the woman remains permitted to the first, but for the House of Shammai the court would have to force the second to write a bill of divorce.. In that case, the House of Shammai should marry women from the House of Hillel since they concede to them. But the House of Hillel should not marry women from the House of Shammai since they do not concede to them. Rebbi Hila in the name of Rebbi Joḥanan: They all followed the same practice²⁵²Following the House of Hillel.. If they followed the same practice, in this case we stated²⁵³Mishnah Miqwa’ot 4:5. If there is a trough in a rock too small to be a miqweh (40 seah), one may drill holes in the rock to lead the water to a miqweh. The House of Hillel require that the hole be slightly more than 2 fingers in diameter; the House of Shammai require that most of the bottom be removed. In a case in Jerusalem known as “trough of Jehu”, the House of Shammai actually did enlarge the hole even though practice should follow the House of Hillel.: “The House of Shammai sent and diminished it, since the House of Shammai says unless most of it is missing?” Rebbi Yose ben Rebbi Abun said, the House of Shammai acted before the question came before the House of Hillel. After a question came before the House of Hillel, the House of Shammai were not touching it. Rebbi Abba Mari said, that is correct. Did we not state²⁵⁴It is unknown where this is stated.: “They declared impure all purities from before”, but not in the future. Rebbi Yose ben Rebbi Abun said, Rav and Samuel, one said both acted according to valid practice²⁵²Following the House of Hillel.; the other said, each party followed its own practice. Bastardy is between them and you say so? The Omnipresent watched and no case ever happened²⁵⁵The Babli, 14a, disagrees and holds that they informed one another in case the child of a family should not be married by a person of the other House. Since the ascendancy of the House of Shammai was so shortlived, the position of the Yerushalmi seems justified. One has to wonder what the rules were for marriages between Sadducees and Pharisees in late Temple times..