Niddah 6 - The Kohen's Portion of Thanksgiving
If a woman finds a stain of blood on her clothing, she conveys ritual impurity retroactively. This is because it might be uterine blood, and it is not known when it came. This case is thus stricter than the previous ones we discussed. To what does this ritual impurity applies? To food and drinks. However, it is only a doubtful impurity, imposed by the Sages as a precaution, thus although the foods are not eaten, they cannot be burned either - as is done with regular holy foods that became impure.
This impurity imposed by the Sages applies only to the holy foods of the Temple, but not to regular foods. Rav Huna added that it does not apply to terumah - the Kohen's portion of the produce. They challenged Rav Huna based on the following story.
It happened that a maidservant in the house of Rabban Gamliel was baking breads of the Kohen's portion. Between every loaf, she would wash the hands and examine herself. After the last loaf she discovered that she was impure, and Rabban Gamliel rules all the bread impure. She argued, "Didn't I examine myself after every loaf?!" - and Rabban Gamliel said, "If so, they are all pure." In this story, the breads were terumah, Kohen's portion, and impurity applied! - while Rav Huna said that it should not!? Rav Huna would say, "It was the portion given to the Kohen from the thanksgiving offering."
Art: Pietro Ricchi - A Maidservant With A Boy In A Larder, A Still Life Of Artichokes, Lemons And Other Kitchen Equipment On A Table Beside Them