After a woman gives birth, she is considered ritually defiled for a period of time, after which she is obligated to bring sacrifices to the Temple that would allow her to complete her ceremony of purity and once again eat sacrifices and so forth (see Vayikra 12:6-8). The sacrifices that were brought included a burnt-offering and a sin-offering. While the burnt-offering could have been a lamb, the Torah also allowed for her to replace it with two turtle-doves, or two young pigeons, and it was common practice for birds to be brought as the sacrifice.
Since women are not commanded to visit the Temple at each of the pilgrimage holidays, oftentimes years went by before a woman would visit the Temple and bring her sacrifices. It was therefore not uncommon for a woman to visit the Temple after a series of births. The Mishnah on today’s daf (=page) teaches that a woman who had given birth several times and then visits the Temple was obligated to bring a set of sacrifices for each of her births. This led to a rise in the price of these birds, which was a great hardship for the women. The Mishnah relates:
It once happened in Jerusalem that the price of a pair of doves rose to a golden dinar. Said Rabban Shimon ben Gamliel“by this sanctuary, I shall not go to sleep tonight before they cost but a silver dinar!” Then he entered the bet din and taught: if a woman had five certain births or five certain issues she need bring but one offering, and may then partake of sacrificial meat, and she is not bound to bring the other offerings. Thereupon the price of a pair of birds stood at a quarter of a silver dinar each.
Rashi explains that Rabban Shimon ben Gamliel agreed that the true biblical obligation was to bring a sacrifice for each and every birth, but felt that a change needed to be made based on the logic of “It is time for the LORD to work; they have made void Thy law” (Tehillim 119:126). Some suggest that Rabban Shimon ben Gamliel argues with the other opinions, ruling that there is no real requirement for separate sacrifices for each birth. According to the Ritva all agree that there is no biblical requirement to bring a separate sacrifice for each birth, rather it was a rabbinic enactment that Rabban Shimon ben Gamliel voided.