Sotah, Chapter 9, Mishnah 14. This mishnah deals with several of the decrees that were enacted in the wake of the various wars against Jerusalem in the era of the destruction of the Second Temple.
"B'pulmus shel Aspasyanus" - in the war of Vespasian:
"Gazru al atros chasanim" - during the war that Vespasian waged against Jerusalem, the Sages decreed against certain types of crowns that people were accustomed to provide for grooms at their weddings. Because of the troubles and hardships of the time, they did not want celebration on such a scale.
"V'al ha'irus" - they likewise decreed against the use of a certain type of musical instrument.
"B'pulmus shel Titus" - in the war of Titus:
"Gazru al atros kallos" - during the war waged by Titus, the Roman general, they decreed as well against the crowns that people were accustomed to hold for brides.
"V'shelo yilmad adam es b'no Yevanis" - this does not refer to the Greek language, but to a particular type of wisdom, Greek wisdom, which included certain methods of conveying coded messages.
The origin of the decree against Greek wisdom:
The Gemara explains, based on a beraisa, that this enactment was actually made many years earlier, during the civil war that broke out between the houses of the Hasmoneans. Those besieging Jerusalem were Jews, and they wanted to supply offerings for the Temple: the people of the city inside would lower money down, and the besiegers would send up lambs for the daily Tamid offering.
However, one elder inside the city, who was apparently a wicked man, knew how to communicate through that Greek wisdom and its method of conveying messages. He hinted to them that as long as the offerings were being brought up they would not be able to conquer the city, because of the spiritual strength that the Temple service provides, and therefore they should send up a pig instead of the lamb - and so they did. At that moment the Sages declared: "Cursed is the man who raises pigs, and cursed is the man who teaches his son Greek wisdom."
Even though this took place long before the era of Titus, the Sages understood that the decree from those earlier years did not hold, and only in the days of Titus did it take on real halachic force.
The decree of the "pirion":
The mishnah continues: during the final war of Titus against Jerusalem, they decreed that a bride should not go out in a pirion - a sort of canopy-like structure, made of golden garments, that was prepared for the bride as she traveled from her father's house to her husband's house as part of the joy of the wedding. They therefore decreed that she should not use it at that time.
"Raboseinu hitiru" - the mishnah concludes that our Sages permitted her to use the pirion, and the Gemara explains the reason: because there is an element of modesty involved, and therefore they restored the practice and reinstituted it.
In summary: in this mishnah we learned about the decrees enacted in the wake of the wars against Jerusalem - in the war of Vespasian: grooms' crowns and the irus; in the war of Titus: brides' crowns and the study of Greek wisdom, whose origin lies in the days of the civil war between the houses of the Hasmoneans and the incident of the pig; and in the final war: the decree of the pirion, which our Sages permitted for reasons of modesty.