Beitzah, Chapter 5, Mishnah 4. We continue our discussion of the laws of techumin, and now we turn to the status of vessels and ingredients that are borrowed on Yom Tov: whose techum determines where they may go.
One who borrows a vessel from his friend:
"HaSho'el kli mechaveiro me'erev Yom Tov - keraglei hasho'el" - the techum of the vessel is determined by the techum of the borrower, since the loan took place before Yom Tov began. The laws of techumin take effect with the onset of Yom Tov, and at that moment the vessel was already in the borrower's possession.
"BeYom Tov - keraglei hamash'il" - the techum of the vessel is determined by the techum of the lender, because at the start of Yom Tov the vessel was still in his possession.
A woman who borrowed from her friend:
The Mishnah continues: "Ha'ishah shesha'alah mechavertah tavlin umayim umelach le'isatah - harei elu keraglei sh'teihen" - a woman who borrowed spices, water and salt from her friend for the dough she is preparing: the dough takes on the status of both women together. What this means in practice is that the dough may be carried only in the area where the two techumin overlap, that is, in the place where both women are permitted to walk. If their techumin differ, that overlap is the only place to which this dough may be taken on Yom Tov.
The view of Rabbi Yehudah:
"Rabbi Yehudah poter bamayim" - in Rabbi Yehudah's view, the status of the dough is not determined by the water. If a woman borrowed water from her friend, this presents no problem, since water inside the dough is not recognizable and is not considered significant enough. It loses its independent status and is nullified in the dough, and therefore the lender's contribution does not determine the techum.
Regarding salt, however, Rabbi Yehudah does not disagree, because the Mishnah is speaking of coarse salt, which is recognizable and noticeable in the dough. Had it been fine salt that dissolves into the dough, Rabbi Yehudah would have given it the same status as water: nullified in the dough, with the lender's contribution carrying no significance.
In summary: in this Mishnah we learned that a vessel borrowed before Yom Tov follows the techum of the borrower, while a vessel borrowed on Yom Tov itself follows the techum of the lender, everything depending on where it was located when Yom Tov began. We also learned that dough made from borrowed spices, water and salt takes on the techum of both women, and may be moved only within the area common to them both. Rabbi Yehudah exempts in the case of water, which is nullified in the dough, but he agrees regarding coarse salt, which remains recognizable within it.