• For what sort of water source can pasei biraot be made
• Fencing in an area with no residential facility
• Size of the Mishkan courtyard and its application to such an area
• Difference between sowing and planting in such an area
• Changing the status of such an area through construction
• Size of fenced in area and the lesson learned from Prophet Yeshayahu
• The courtyard neighbor who forgot to make an eiruv
• Which foods qualify for use as eiruv
• How to relate to generalities in the Mishna
• Which foods may be purchased with funds used for redeeming Second Tithe
• Halachic and medical status of certain plants
• The quantity of foods needed for use as eiruv
• Wine and beer in regard to eiruv and mikveh

• Eiruvin 27

Food plays a central role in regard to the making of an eiruv chatzeirot by all the neighbors contributing to food placed in one of the homes, which enables them to carry on Shabbat in their courtyard area, and for eiruv techumim, which enables one to walk on Shabbat beyond the normal limitation. In regard to maaser sheini (second tithe of crops which must be consumed in Yerushalayim or redeemed for money which must then be used for acquiring food in Yerushalayim), the funds must be spent only on something considered food.

A parallel is drawn in the mishna (26:6) between the food matters which qualify for making an eiruv and which may be purchased with the funds used for redeeming maaser sheini crops. Nevertheless subtle differences do arise.

One of them is in regard to the status of salt water. The mishna states that neither water nor salt qualifies as food for eriuv or Second Tithe purposes. Rabbi Yitzchak, however, states that if salt and water are combined and some oil is added, this mixture can be used for the purpose of the maaser sheini funds. The gemara posits that he will certainly consider such a combination as qualifying for an eiruv because the requirements there are less demanding.

Tosefot challenges this assumption by pointing out that mushrooms can be purchased with maaser sheini funds and yet cannot be used for an eiruv. His resolution is to distinguish between the requirements in either category. There is no question that a lower degree of food is necessary for making an eiruv but it must be food that is edible at the beginning of Shabbat when the eiruv takes effect. Although uncooked mushrooms, because of their inedible nature in the raw, cannot be used for an eiruv, they qualify as food for maaser sheini purposes since they are edible after cooking. The salt wateroil combination which is readily usable for consumption qualifies not only for Second Tithe but surely for an eiruv as well.

"We cannot assume from a general rule stated in the mishna that there are no exceptions to that rule, and even when some exceptions are explicitly named, there may still be others."

• Rabbi Yochanan - Eiruvin 27a