Introduction to Tumah and Taharah
There are six distinct aspects to Tumah and Taharah. First, being the sources of Tumah. Second, the severity of Tumah. Third, its modes of transmission. Fourth, the susceptibility of a person or item to becoming Tamei. Fifth, a person or item's sensitivity to Tumah. Sixth, purification rituals. The rules are complex and the exceptions more so. Seder Taharos generally concerns itself with these issues. Below is brief introduction to these topics.
Sources of Tumah
The Torah describes a number of sources of Tumah which can be broken down into two basic categories. The first, are external sources of Tumah, such as humans (Tumas Meis) and certain animals (N'veila) and rodents (Sheretz) that have died. These items are by their very nature Tamei and coming in contact with them will make a person Tamei. The second category are situations where the person internally, due to a change in his own body, becomes Tamei (i.e., the Tumah flows from the person himself). Examples of this include, a Zav, Zavah (Niddah), Yoledes and a Metzorah. These persons have the power to transmit Tumah as well.
Severity of Tumah
Not each source of Tumah is created equal. A corpse is the highest level of Tumah and is called an Avi Avos HaTumah (the ultimate source of Tumah). Its severity is most notable in the way it transmits Tumah and its purification ritual (i.e., sprinkling of the Mei Chatas--spring water mixed with ashes of the Parah Adumah). Most other sources of Tumah are called Avos HaTumah. Their severity can be seen by the fact that certain fluids that emanate from their bodies (e.g., saliva) are Avos HaTumah as well.
Importantly, as Tumah is transmitted from one person or item to another, it typically steps down a level of severity. Therefore, if an Av HaTumah touches a person or item, the person will become a Rishon (first derivative). A Rishon will create a Sheini (second derivative). A Sheini will create a Shlishi (third derivative). A Shlishi will create a Revi'i (fourth derivative).
There are, however, certain exceptions to the step down in severity paradigm. First, in certain instances the transmitted level of Tumah remains the same, i.e., an Av HaTumah will make the recipient an Av HaTumah as well (I.e., Tumas Midras--a cushion on which a Zav sits will likewise be an Av HaTumah capable of transmitting Tumah). Second, certain Avos have the power, so long as it remains in direct contact with a person, to turn that person temporarily into an Av HaTumah as well (טומאת חיבורין). Finally, the Chachomim decreed that liquids, even when touched by a Sheini, will always be a Rishon, with the capabilities of even making a vessel Tamei.
Modes of Transmission
The most typical mode of transmission is via touch. If an Av Hatumah touches a person the person will become a Rishon. If that person then touches an apple, the apple will become a Sheini. Similarly, if a person wearing a glove touches a Sheretz--an Av Hatumah--the glove will be a Rishon and the person will be Tahor.
In addition to direct touch, a corpse's Tumah spreads via Tumas Ohel in one of three ways (i) by being under the same roof as the corpse, (ii) the corpse hovering over a person or (iii) a person hovering over the corpse. In the case of being under the same roof, everything in the house will become Tamei. The one main exception are earthenware pots (Klei Cheres). These cannot become Tamei via touch on the outside; rather only by their interior space being exposed to Tumah (therefore, if it sealed in a house that has a corpse in it, the vessel and its contents, if sealed, will remain Tahor).
A Zav, Zavah, Yoledes and Metzorah can also transmit Tumah via leaning on an item, carrying (even without touching) and item or being carried by an item or person. These laws are very complex and can be found in the final chapter of Mesechtas Zavim.
Susceptibility to Becoming Tamei
There are differences between a person's, Keilim's and food's susceptibility to Tumah. People and most non-food items are susceptible to Tumah at any time. No preconditions exists. Whereas, a vessel will only become susceptible to Tumah when it is close to its finished state (i.e., a flat piece of wood is not susceptible to Tumah).
Food's susceptibility to Tumah is far more complex. The Chachomim learned that prior to becoming susceptible to Tumah, it first must have become consciously wet (i.e., washed with water or other liquid). In language of the Mishna, Huchshar L'Kabel Tumah. Therefore, if after picking an apple off the tree you guard it from ever becoming wet, that apple is not capable of becoming Tamei.
Sensitivity to Tumah
Sensitivity to Tumah is a influenced by both the type of item and its intended purpose. At its most basic level, Tumah will not extend beyond a Rishon and in rare occasions a Sheini. So, for instance, a person and Keilim, can only become Tamei from an Avi Avos or an Av Hatumah so that they will become at worst, a Rishon. There is no Sheini L'Tumah for a person. (A Keili can under certain circumstances stances become a Sheini if touched by a liquid Rishon).
Foods are more sensitive to Tumah and can become a Sheini. Liquids, being even more sensitive, per the Chachomim, will always remain a Rishon.
The above rules are for Chullin, non-consecrated food. However, the Chachomim identified a number of levels of sanctified foods and liquids that, given their levels of Kedusha (holiness), are more sensitive to Tumah--and hence, more susceptible as well. These levels are as follows:
- Ma'aser Sheini (the Second tithe). It was brought to Yerushalyim and was to be eaten in a state of Taharah.
- Terumah: The portion of the crop given to the Kohein. It could only be eaten by the Kohein and his family. It's holiness level made it susceptible of becoming a Shlishi L'Tumah.
- Kodshim: sacrificial meat and bread. It's holiness level made it susceptible of becoming a Revi'i L'Tumah
- Mei Chatas: at its core, the heightened level of holiness and its sensitivity to Tumah made it so that there was no limit to levels of Tumah to which it was susceptible. In other words, so long as there was somewhere in the chain some very low level of Tumah, it gets passed along as if it were a severe Tumah--despoiling the Mei Chatas.
The corollary to this sensitivity to Tumah is the requirement that a person likewise take more focused and, at times, stringent, measures when purifying himself prior to consuming and/or handling each successive level of consecrated food. What works to ensure purity for Terumah may not work for Kodshim. As you move up each level in purity, it demands more scrutiny in the chain in purity.
It is this sensitivity that is the topic of the next three Mishnayos. Mishna 2:5 describes the added precautions added to maintaining "pure" hands. Mishna 2:6 highlights the fact that purifying oneself for each successive level of Kedusha requires specific intent. Mishna 2:7 describes a precaution followed to maintain heightened levels of purity.
Purification Rituals
Once Tamei, a person and/or most items will remain in its impure state until it undergoes a purification ritual. These diverse rituals will depend on the source and level of Tumah trying to be cleansed. The most typical form of purification ritual is submerging oneself or item in a Mikvah, a standing pool of water of a particular size and volume. This works for most situations. For some forms of Tumah, rather than a Mikvah, the source of water must be a flowing spring of water. Finally, cleansing Tumas Meis requires, in addition to submersion in a Mikvah, the sprinkling the Mei Chatas on the person or item.
Notably, earthenware vessels cannot be cleansed of Tumah except by shattering the vessel. In addition, food cannot be cleansed in any instance.