These are some basic observance rules of Judaism that your characters may or may not follow. I used to have these at the bottom of the Passover post, but it made more sense to put them into their own separate post.
The No Work Rules
The most Orthodox rules for keeping the Sabbath and major holidays, aka the “no work rules”:
No work, which includes a whole bunch of things, many of which you will see in the next bullet points
No actual work - as in, job and school
No driving/riding in a car
No using money (some Jews are even uncomfortable with fake money)
No carrying things outside of your house or a designated eruv (an area that has a completely ritual enclosed border surrounding a neighborhood and therefore counts as one private dwelling - modern eruvim often use things like telephone wires and ropes)
No using electronic devices
No writing
No farming
No cooking
No starting a fire
No playing musical instruments
No getting married or holding funerals
No doing a bunch of other things that modern people generally leave to professionals, such as trapping and slaughtering animals
If I’ve mentioned the “no work rules” in another post (I’ll try to make sure they all link properly), it refers to these, because they apply on a number of Jewish holidays - specifically, Shabbat, parts of Passover, Shavuot, parts of Sukkot, Rosh Hashanah, and Yom Kippur.
All of these rules can be ignored IF AND ONLY IF doing so is pikuach nefesh - that it will save a life. So a super observant Orthodox Jew can and will use a phone to call an ambulance to take someone having a heart attack to the hospital on Shabbat. But once they’re at the hospital, they can’t drive back on Shabbat, because doing so doesn’t save a life anymore.
There’s one other exception, but we’ll get to that in the life cycle section.
Non-Orthodox Jews DO NOT always keep all of these rules. For instance, I absolutely write and use computers and transportation on Saturday. I would essentially have to claim a religious exemption to get out of working on Saturdays, and that’s not worth it to me.
It’s all in your character’s level of observance and what they consider a priority.
Fast Days
In Judaism, there are two types of fast days: major and minor. Major fast days (Yom Kippur and Tisha B’Av) last from sunset to sunset while minor fast days (Ta’anit Bechorot, Tzom Tamuz, Tzom Gedaliah, Asara B’Tevet, and Ta’anit Esther) last from sunrise to sunset.
In both cases, nothing can be consumed, including food and drink. That includes water. Which means Yom Kippur is 25 to 25 ½ hours with no food or water. Yom Kippur follows the no work rules; all other fast days do not.
If you are not healthy and need to eat or drink for medical reasons, you are expected to eat or drink as needed, but no more than needed (so skip that piece of cake). This includes anyone who takes medication that requires food, pregnant women, and women who are nursing. Children under the age of 13 are not expected to fast.
Your characters may or may not observe all fast days. If they do one, it’s going to be Yom Kippur. If they do more than one, the second is likely to be Tisha B’Av. Others are very unlikely for most modern American Jews who aren’t Orthodox or clergy. So while it’s useful to have the info, keep in mind that it may not be observed.
Everyday Laws of Kashrut (Keeping Kosher)
This will be discussed in more depth in a food post in the future (seriously, I’m definitely doing a food post), but for now I’m putting this here.
No mixing meat and milk (some people extend this to waiting as much as six hours after meat before eating milk, because they mix in your stomach) (birds and mammals count as meat, fish counts as pareve aka neither meat nor milk, eggs count as pareve as well)
Only fish with fins and scales (no shellfish, no eel, no shark, you can debate swordfish and tuna because it has scales in some stages but not others)
No birds of prey or scavengers
Only mammals that chew their cud AND have cloven hooves (generally this means beef, lamb, venison are all fine, but pork definitely isn’t and neither are less commonly eaten mammals)
No blood
Even if it’s a kosher animal, it must have been killed kosherly and be certified