Aside from the first and second Temples in Jerusalem, the only other Jewish Temples where sacrifices were brought were built by Jewish priests in Egypt. The Mishna on today’s daf teaches that someone who pledged to bring a sacrifice must bring it in the Temple in Jerusalem, and not in Beit Honyo – the Temple of Onias. Even if the person specifically committed to bringing the sacrifice there he cannot do so, rather he must bring it in Jerusalem.
The Gemara quotes a baraita that brings two opinions about the Temple of Onias. According to Rabbi Meir, that temple was a place of pagan idol worship; Rabbi Yehuda rules that only Jewish sacrifices to God were brought there.
According to Josephus, the Temple of Onias was built in Leontopolis in Egypt by the son of the High Priest Onias III, sometime around the year 155 BCE. This temple was modeled after the Temple in Jerusalem. According to the Talmud (Menaḥot 109b), Onias fled from Jerusalem to Egypt following a serious dispute with his brother. According to Josephus, the matter was connected with the Hellenists in Jerusalem, and, after a time, with the Hasmonean dynasty that claimed the High Priesthood in Jerusalem.
As we have learned, there is a disagreement about how to view the Temple of Onias, where the priests who served were all true priests – descendants of Aharon HaKohen. It appears that the accepted position is that this was not a house of pagan worship; the most serious problem with it was the fact that a temple where sacrifices were brought that existed at the same time as an operating Temple in Jerusalem is forbidden, and participating in the sacrificial service there was punishable by karet (a serious heavenly punishment). For this reason, kohanim who served there were not welcome to serve in the Temple in Jerusalem.
According to Josephus, Vespasian closed the Temple of Onias about three years after the destruction of the Temple in Jerusalem, but it is possible that the service there was revived at a later time.