Chapter 4, Mishna 5
One who is heading home as Shabbos is about to start, and he knows 1) his house is 4000 cubits aways and 2) there’s a particular tree 2000 cubits away in the road home, can declare his Shabbos dwelling “is beside the trunk of the tree,” and he’ll be able to walk home on Shabbos. But if he says his home is “under the tree” he won’t. Yesterday we said the reason is his place is not defined specifically enough. Today we explore an alternative theory: that which can’t be accomplished sequentially, neither can it be accomplished simultaneously. Examples brought from tithing grain, tithing sheep, and consecrating 40 loaves for a thanksgiving offering. Though the declaration “under the tree” is not specific enough, even a much larger space will work if defined by an enclosure, or if elevated/depressed 10 handbreadths from public domain. Shmuel seems to prevail over Rav, but Rav’s ruling still has authority because he is sometimes considered a Tanna.