The egg and I TB Shabbat 43

Today’s daf Shabbat 43 teaches two important principles concerning mukseh (מוקצה). The first principle deals with preparedness. One has to prepare everything before Shabbat for use on Shabbat. If you didn’t have in mind to use the item on Shabbat, you can’t use it on Shabbat because it is mukseh. Mukseh comes the Hebrew root קצה which means side meaning it has been put aside not to be used. Now we can better understand Rav Hisda’s position.


“Rav Hisda said: Although the Sages said that one may not place a vessel beneath a hen preparing to lay an egg on Shabbat on an inclined surface, in order to receive its egg and prevent it from breaking when it falls; however, they permitted overturning a vessel onto an egg on Shabbat so that it will not be trampled and break. (TB Shabbat 42b)


“Rav Yosef said: This is the reasoning of Rav Hisda, who allowed covering a hen’s egg, but not placing a vessel underneath the hen, in order to receive the egg when it is laid: Because by receiving the egg in the vessel, he negates a vessel’s preparedness. Initially, the vessel was available for any use. Since it now contains an egg that may neither be used nor moved, the vessel too may no longer be carried. It is tantamount to breaking the vessel.” (Sefaria.org translation)


The egg is mukseh davka because it came into existence during Shabbat. There was no way you could have in mind to use a non existent egg on Friday for the follow day, Shabbat. When the mukseh egg lands in the vessel, the vessel becomes mukseh on account of the egg. Rashi explains that the vessel is compared to a broken one. Once a vessel is broken and can’t be used for its original purpose, the vessel becomes mukseh.


But if you need the space underneath the mukseh item, one may move it. Once you move it, you can place the mukseh item anywhere you want. This is the second principle.

“Come and hear what was taught in a baraita: With regard to both an egg that was laid on Shabbat and an egg that was laid on a Festival, one may neither move it to cover a vessel with it, nor to support the legs of a bed with it. However, one may cover it with a vessel so that it does not break. This is contrary to Rabbi Yitzhak’s opinion. Here too, it is referring to a vessel that one seeks to move because he requires its location. Since he was permitted to move it from its place, he is also permitted to cover an egg with it.” (Sefaria.org translation)