Pesachim 20 - A needle in a cow, a reptile in an oven
Earlier we said that if a needle is found in the meat of a sacrifice (such as a cow), then that meat is considered impure, while the hands and the knife are pure, and explained the reason for it.
But why should the meat ever become impure? Any food, to become impure, must first become wet with water. While any animal is alive, it cannot become impure, and they have just slaughtered it!? It cannot be any liquid in the Temple, because these are all pure . Nor can it be the impurity declared out of love for holy things, because such impurity was only declared on object themselves, not giving them the power to transmit impurity further. Rav Yehudah gave an answer: the owner led the cow through a river on the way to the Temple, to wash it off, and this water was still dripping. Since the owner wanted this water to be on a cow, all precondition for impurity are fulfilled.
The Talmud suggests and refutes a hypotheses about impurity. If a dead reptile is found in an earthenware utensil, it makes the utensil impure. Can we view the utensil as being full of impurity, contaminating any food that is inside? - No, we cannot. The Torah said, "anything inside," which tells us that food are impure by virtue of being inside. Thus, we have to say that the reptile touches the air, and the air touches the food, resulting in a lesser degree of impurity.
Art: Peasant Woman Watering Her Cow by Jean-Baptiste-Camille Corot