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The Mishna (73a) lists ‘shocheit’ (slaughtering) as one of the 39 avos melachos on Shabbos. The Mishna (107a) teaches that one who is chovel or causes a wound in a person or animal has violated a melacha on Shabbos. There are many opinions amongst the rishonim which melacha one who does chovel is liable for. The Rambam (Shabbos 8:7) writes that one who is chovel has violated dosh (threshing), because when a wound is caused, blood is removed from a person’s capillaries, which is similar to the threshing process. In contrast, Tosafos (75a D”H ki) writes that one is liable for shocheit. Tosafos explains that the pasuk states “ki hadam hu hanefesh” that blood is the location of a person’s soul, and one who causes a person to have a wound removes a bit of the soul, which is equivalent to the melacha of shocheit.
The Shulchan Aruch (316:8) does not take a firm stance on whether to rule in accordance with the Rambam or Tosafos, however, the commentaries on Shulchan Aruch appear to hold like Tosafos (see Magen Avraham [316:8] and Mishna Brurah [316:29], see also Beis Yosef [316:8] who also appears to side with the opinion of Tosafos).
A common example of a situation where the melacha of shocheit becomes relevant is when doctors wish to draw blood from patients. In situations where the blood is part of the general circulation and is needed by the doctor (to perform a blood test or the like) then serious questions of shocheit do exist, which may prohibit a doctor from drawing blood unless there is pikuach nefesh. In contrast, if either the blood or fluid needed is not part of the general circulation, or if a needle must enter a person’s skin but no blood actually needs to be removed for the procedure to be effective, then there may be more room to be lenient to administer such a procedure for a choleh shein bo skana since shocheit wouldn’t apply to such blood. All doctors should consult their respective rabbanim for guidance on how to deal with these and similar questions that relate to their field of work.
- The Gemara Ketubot 5b states that there is no issue of Shocheit if the blood is mifkad pakid. Rashi s.v. mifkad explains that blood that is mifkad pakid stays collected in a certain valve and isn’t absorbed into the flesh. The language of “not part of the general circulation” is borrowed from Rav Schachter’s translation of mifkad pakid regarding Tosfos Shabbos 75a s.v. ki.
- Even though there is no issue of Shocheit, nonetheless, there is a rabbinic issue of creating a hole (Ketubot 5b, Shabbos 107a, Rambam Shabbos 23:1). For a choleh shein bo sakana, it may be permitted (S”A 328:17).