View source for Items That Cannot Be Nullified

==Complete Natural Items (Biryah)==
# If a whole item from a living being is mixed into a mixture it isn’t nullified even one in a thousand<ref>Chullin 100a says that the sciatic nerve isn’t nullified when in a mixture of other sinews because it a complete item. From here the rishonim extrapolate that all complete items are considered significant and not nullified. This is codified in the Rambam (Maachalot Asurot 16:6), Tur, and Shulchan Aruch YD 100:1. 
* Rash (Mishna Trumot 10:8) writes that a complete living item is nullified with an amount 960 times greater than its volume of permitted ingredients. The Rashba (Torat HaBayit 14b) agrees. However, the Rosh (Chullin 7:37) and Ran (Chullin 32b) disagree and say that the mishna Chullin 96b compares the piece that is used to honor guest and a complete item from a living being and a piece that is used to honor guest isn’t nullified even one in a thousand. Shulchan Aruch YD 100:1 and Gra 100:5 rule that a complete item from a living being isn’t nullified even one in a thousand.</ref>, whether or not it is mixed with like or unlike ingredients.<ref>Torat Chatat 40:6 and Taz 101:12 in response to the Isur Veheter HaAruch 25:17</ref> For example, an ant, non-kosher bird, sciatic nerve, and a limb that was detached from a kosher animal are considered whole items and not nullified. <ref>Shulchan Aruch YD 100:1</ref>
# A item from a living being is only considered significant and not nullified if it meets 4 conditions: 
## It comes from a living being.<ref>Gemara Macot 17a sites the opinion of the Rabbis who disagree with Rabbi Shimon that only a complete item from a living being is significant. The Ritva (Chullin 100a) and Taz 100:1 point out that the significance of a living being found in the area of Malkot, as is the subject of the discussion between Rabbi Shimon and the Rabbis, is applied on a rabbinic level to nullification. The idea that only a living item is significant for the halacha of biryah is mentioned by the Ran (chullin 36a s.v. garsinan) and Shulchan Aruch 100:1.</ref>
## It is whole and not cut up.<ref>Ran (chullin 36a s.v. garsinan), Shulchan Aruch 100:1</ref>
## It is forbidden from its creation.<ref>Ran (chullin 36a s.v. garsinan), Shulchan Aruch 100:1</ref>
## If it were to be split up it would lose its unique name.<ref>Rosh (Chullin 7:33), Shulchan Aruch 100:1. All four of the above conditions are summarized by the Pri Megadim (S”D 100:3).</ref>
# An egg with a blood spot potentially is considered a biryah. <ref>The Bet Yosef 110:1 is unsure in understanding the Rambam where just an egg that has an unborn chick is considered a biryah or even an egg with a blood spot is considered a biryah. In the Bedek Habayit he concludes leniently that the egg with a blood spot isn't considered a biryah. The Shach 101:2 argues that it certainly isn't a biryah since it was never a living being. This seems to be the opinion of the Rashba [http://www.hebrewbooks.org/pdfpager.aspx?req=9381&st=&pgnum=209 (Torat Habayit Hakatzar 8a)]. See further in the Bet Yosef 86 and Rambam (Maachalot Asurot 15:19) who implies it is a biryah.</ref>
# If there is a halachic doubt if an item is a biryah it can be nullified, however, if there is a doubt if an item is forbidden but certainly is considered a biryah the item isn't nullified.<ref>Isur Veheter HaAruch 25:7, Taz 100:1</ref>

==Important Foods used to Honor Guests==
# An important piece of food that can be used to honor a guest isn't nullified even one in a thousand.<ref>Shulchan Aruch YD 101:1</ref>
# If there is a halachic doubt if an item is an important piece it can be nullified, however, if there is a doubt if an item is forbidden but certainly is considered an important piece the item isn't nullified.<ref>Isur Veheter HaAruch 25:7, Taz 100:1</ref>

==Items which will become Permitted==
# An item which is either inevitably going to become permitted after some time or it is possible to for you fix it, isn't nullified.<ref>Rashba [http://www.hebrewbooks.org/pdfpager.aspx?req=9381&st=&pgnum=218 (Torat Habayit 12b)], Tur and Shulchan Aruch 102:2. Shach 102:7 writes that everyone agrees to this definition and proves it from the Gemara Beitzah 3b. Shach 102:8 cites the Maharshal who argues that someone which can be fixed but won't become permitted on its own isn't considered an item which will become permitted. The Shach proceeds to reject on the Maharshal because of the case of [[neder]].</ref>
# Something that is forbidden to a person because of a vow is considered an item that will become permitted since one could or should nullify one's vow by annulment.<ref>Gemara Nedarim 59a, Isur Veheter HaAruch 25:4, Shulchan Aruch YD 216:9, Rama 102:4</ref> 
# An egg born on Shabbat or Yom Tov is considered an item that will become permitted since it is permitted after Shabbat or Yom Tov.<ref>Gemara Beitzah 3b, Isur VeHeter HaAruch 25:4, Tur and Shulchan Aruch YD 102:1</ref> The same is true of all [[muktzeh]].<ref>Isur VeHeter HaAruch 25:4</ref>
# If a food will get ruined before you can wait for it to become permitted that it isn't considered an item which will become permitted.<Ref>Gemara Beitzah 4b, Rashba (Beitzah 4a s.v. Ha Deamrinan), Shulchan Aruch 102:4</ref>
# An item which will become permitted isn't nullified even if it isn't whole.<ref>Shulchan Aruch YD 102:1</ref>
# There is a major dispute if the absorbed taste from an item which will become permitted can be nullified. <ref>The Rama 102:4 holds that the taste of an item that will become permitted can be nullified, even if the actual forbidden item was dissolved into the permitted food. The Rama is based on the Isur Veheter 25:17 and 25:19, yet see Shach 102:9 who disputes this interpretation of the Isur Veheter. Hagahot Ashri (Avoda Zara 5:29) is explicitly of this opinion. The Taz 102:9 argues that only taste from a forbidden item that will become permitted can be nullified, but not if the actual item dissolved into the permitted food. The Shach 102:9 holds that all taste from an item that will become permitted cannot be nullified.</ref>
==Sources==
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