At time of Churban, people in Jerusalem were not honest about business but they were honest about not being able to fill positions as Rabbis bc they were unlearned .

Even though Chazal restricted saving more than 3 meals for a fire, one could save a whole basket even if there’s many meals bc his effort is limited to one single act. According to one opinion, it’s always permitted to save more than 3 meals as long it’s to the immediate courtyard and the restriction is only to another courtyard. After some deliberation, the gemara ruled that one may exert effort to gather a lot of good into one cloak and then carry out the cloak. The Rabbis only prohibited removal in several utensils.

One can tell other people to save food for themselves. They can technically keep all the food for themselves bc it’s hefker but God fearing people wouldn’t take it for free. So they return the stuff to the owner after Shabbos and they have the right to ask for compensation and it’s not against the laws of שכר שבת bc it was not discussed on Shabbos as a job.

One can save clothing as well. R Meir allows one to wear as much stuff as they possibly can but r Yosi only allows one to wear what it normal to wear. However, bc it’s being worn and not carried, the Rabbis allowed him to make many trips and save more and more clothing. He can therefore even tell other people to come help save stuff for him.

There a dispute if one can cause extinguishing on Shabbos or not. One Tanna allows it- like spreading a moist goats hide over a closet that fire has taken hold of, or even putting water on a side of a cloak where fire is on the other side, or making a wall in front of fire with utensils fill of water that may burst when the fire comes and extinguish the fire. R Yosi does not agree and he prohibits causing fire to go out on Shabbos. The gemara explains the concept behind this is the language in the Torah לא תעשה- into direct actions are melocho, but causing melocho is ok. R Yosi through is scared the frenzy may lead to putting out fire.

Another context of doing vs causing is when someone has a name of HaShem written on their skin and they have to go to the mikveh. It will cause the name of HaShem to be erased but it’s not a direct act of erasing. Bc the language of the pasuk is לא תעשון, there’s no problem of causing the name to be erased. Everyone agrees it’s preferable to cover the name with a piece of reed so one isn’t naked in front of Hashem’s name. There’s a dispute if one should should look for a reed if they have a mitzvah to go to the mikveh right now or just try to cover it with their hand. The root of the issue is whether it’s a mitzvah to go to the mikveh on time.

When a lamp is behind a door, one has to be carful that they don’t put out the fire by moving from the wind. Even though it’s not the intent but it’s a psik reisha.