Niddah 10 - Laws of a Very Young Girl
The following deals only with the laws of purity in regard to the Temple and foods that need to remain ritually pure. If a young girl whose time to discharge blood has not yet arrived - that is, she has not reached the age - discharged blood, then the first time she has the presumption of ritual purity, and all foods that she handled prior remain pure. After the second time she is still not given retroactive impurity, and only after the third time she has the law of all other women, and the foods that she handled become retroactively impure, back to the time of a previous check, but no more than twenty-four hours back. If she then misses three periods, she has the presumption of purity again. This, however, is only the opinion of Rabbi Eliezer, who states that three missed periods remove her from retroactive impurity.
It once happened that such a case came to the court of Rabbi Yehudah the Prince, and he ruled the foods pure, which agrees with the opinion of Rabbi Eliezer. Afterwards, Rabbi Yehudah recalled that the Sages disagreed with Rabbi Eliezer, and it bothered him. However, he then confirmed his ruling, saying that Rabbi Eliezer is great enough to rely on his opinion at the time of pressing need. What was the pressing need? Some say that it was the time of a famine, and the foods that she handled were such that they could not be eaten should they become impure. Others say that she has handled massive amounts of food, and making them impure would result in a large loss.
Art: Peder Vilhelm Ilsted - Girl Reading a Letter in an Interior