הלכות טומאת אוכלין

Water that is in a container contracts impurity, whether it entered the container willfully or against one's desires. It imparts impurity to foods and keilim whether it came in contact with them willfully or against one's will. Water collected on the earth, by contrast, e.g., water in a cistern, storage trench, or storage cavern or water in a pit that does not contain 40 se'ah, does not contract impurity unless it comes in contact with the source of impurity willfully, nor does it impart impurity unless it comes in contact with the food willfully.
What is implied? When there was less than 40 se'ah of water collected on the ground, whether it was drawn or it was not drawn, and a human corpse fell into this water or an impure person walked through it, it is pure. If, however, an impure person drank from this water, one filled an impure container with it, or impure liquids willfully fell into it, the water becomes impure even though it is still collected on the ground. If a pure person drank from this water after it became impure on the ground or one filled a pure container with it, the person who drank and the container with which the water was drawn becomes impure, because he drank or the container was filled intentionally.
If a loaf that was terumah fell into such water, it is pure as it was originally, because the water imparts impurity only when foods come in contact with it willfully. Therefore, if one washed his hand and removed a loaf, the loaf contracts impurity from the water on the person's hand, because it was removed willfully.

The following laws apply to water that is collected in a pit and other types of water collected on the ground, e.g., water in a cistern, storage trench, or storage cavern, rainwater that stopped flowing and collected in one place or mikveot that do not contain 40 se'ah that became impure. If rain then descended, causing there to be more rainwater than the water originally collected, even if the original water did not flow out, those bodies of water become pure. Therefore, during the rainy season, all water collected on the ground, e.g., water collected in a pit or the like, is assumed to be pure.

Different laws apply when the rains cease. When such bodies of water are close to a town or a thoroughfare, they are impure, because it can be assumed that an impure person drank from them and/or water was drawn from them in impure containers. Those that are distant are pure until the majority of people begin walking. Once they do, they are all assumed to impure, because those who journey on caravans drink from them.
When does the above apply? With regard to water in a pit from which it is possible to drink. If, however, there is water in a pit that it is impossible to drink from except through great effort, it is assumed to be pure unless the footprints of a person or large animal were evident. If, however, the footprints of a small animal were found, the water is pure, because it is possible that the animal descended on its own accord.

In the rainy season, it can be assumed that the mud and the water in the hollows at the entrance of stores in the public domain are pure. When the rains cease, they are considered as drainage water. The ruling concerning water in the marketplace depends on the majority. .
When wine, milk, or honey fall into a pit filled with water, the ruling depends on the majority. When oil falls into it, the mixture can contract and impart impurity without the owner's desire even when it congeals. The rationale is that it is impossible that droplets will not remain mixed with the water.

Streams of rainwater that are still flowing - even if they do not contain 40 se'ah, since they are on the earth and their water is flowing - do not contract ritual impurity. Even if an impure person drank from them, drew water from them with an impure container, or poured impure water into them, they are still pure with regard to all matters.

When a person was eating terumah with impure hands, e.g., a dried fig that had not come into contact with water, if he inserted his hand into his mouth to remove a pebble, were he to turn over his finger while doing so, the fig would become impure because of his saliva. For the saliva would become impure because of the person's hand, because he uprooted the saliva from its place. If, however, he did not turn over his finger, it is pure. The rationale is that, before he turns over his finger or sucks it, the liquid in his mouth is comparable to water on the earth that was not uprooted from its place, but instead, is on the ground. As explained, such water only contracts and imparts impurity due to willful actions. This person desired only to remove the pebble.
The following rules apply when, in addition to the dried fig, there was a pundiyon in his mouth and he extended his hand to remove it and the fig from his mouth. If he had placed the coin in his mouth because he was thirsty, the saliva on it is considered as removed from its place and the fig contracts impurity from the moisture in his mouth that contracted impurity because of his hand.

The following rules apply when a woman was partaking of food that is terumah which had not been made susceptible to impurity while she was removing the coals from an impure oven. If she was poked by a splinter that caused her to bleed and she was sucking her finger because of the blood or she burnt her finger and inserted it into her mouth, the terumah in her mouth contracted impurity, because she desired to remove the liquid from her mouth, taking it [from its place] by sucking her finger.