Before us is Mishnah 2 of the tenth chapter of Maseches Eruvin, and it is a direct continuation of the previous Mishnah. There we dealt with someone who found many pairs of tefillin in a field and cannot bring them all into a private domain before Shabbos ends. We concluded, adding to our Mishnah, that he covers them where they are and comes back to take them after Shabbos - but this applies specifically when the danger that requires covering them stems from a government decree against wearing tefillin, in which case a person must not be seen with tefillin in his hand.
Between a government decree and the danger of robbers:
If, however, the danger comes only from robbers, there is no reason to cover them, since he is permitted to be seen with tefillin and his only concern is the robbers. In such a case he takes all of them at once, and the method is that he walks slightly less than four amos and stops, then again slightly less than four amos and stops, and in this way he never transgresses the Torah prohibition of carrying on Shabbos.
The view of Rabbi Shimon:
Rabbi Shimon in our Mishnah disagrees: "Rabbi Shimon omer: nosnan lechavero vachavero lachavero ad shemagia lechatzer hachitzonah" - Rabbi Shimon says: he hands them to his fellow, and his fellow to another fellow, until they reach the outermost courtyard. Instead of one person stopping every less than four amos, he hands the tefillin to his fellow, and his fellow to another fellow, and so on - so that no single person walks with them at all. Rabbi Shimon is concerned that if we permit a person to walk less than four amos, as the previous Mishnah stated, he may err and walk more than four amos. Therefore they pass them from one to another until they reach the outermost courtyard, which is a private domain, and there the tefillin may be left over Shabbos.
"Vechen beno":
Rabbi Shimon said this not only regarding tefillin, but "vechen beno" - and so too with his son: even if a son was born to him in the field and he needs to bring him to the settled areas, he hands him to his fellow, and his fellow to another fellow, "afilu mei'ah" - even a hundred, until they reach the house, the place they need to reach.
A barrel of water that went outside the Shabbos boundary:
Rabbi Yehudah adds a further law concerning a person who hands an object to his fellow on Shabbos: "Nosen adam chavis lechavero vachavero lachavero afilu chutz lat'chum" - a person may hand a barrel to his fellow, and his fellow to another fellow, even beyond the Shabbos boundary. The case is one of people stranded outside the boundary who need water. The Sages were lenient for them and permitted one person to carry the barrel and hand it to his fellow, and his fellow to another, and that one to another, even though it thereby reaches a place outside the boundary.
At first glance, a person is not permitted to take objects that were within the boundary and bring them outside the boundary. But the Gemara explains that this refers to a barrel of water in which both the barrel and the water inside it are ownerless, that is, they have no owner. And Rabbi Yehudah, who stated this ruling, held that ownerless objects do not acquire a Shabbos resting place - they do not have their own two thousand amos from where they are; rather, whoever lifts them, they acquire the boundary of that person. Therefore, for the one who lifts the barrel, his boundary at that moment is the boundary of the water in the barrel; and with the next person, his boundary is what determines, and so on, until the object reaches a place outside the boundary. There is nothing wrong with this, since each person has a different boundary.
The view of those who disagree:
This was Rabbi Yehudah's opinion, but they said to him that this barrel of water does not travel further than the feet of its owner, since it is bound to its owner. And as we said, there is no actual owner here and the barrel is ownerless; rather, their words follow the view of Rabbi Yose ben Rabbi Nuri earlier in the Maseches, who said that ownerless objects do acquire a Shabbos resting place - they have two thousand amos from the place where they are found, and they cannot leave it. That is why they use the phrase that they do not travel further than the owner, even though there is no actual owner here: the meaning is that we view the object as though it has its own ownership and a resting place of its own, that it rests on Shabbos in the place where it is found, and therefore it cannot leave it.
In summary: In this Mishnah we learned the view of Rabbi Shimon, that passing the tefillin from hand to hand is preferable to walking less than four amos, out of concern that a person will err and walk more than that, and the same law applies to his son who was born in the field - even with a hundred people. We also learned the law of the ownerless barrel of water: according to Rabbi Yehudah, ownerless objects do not acquire a Shabbos resting place and therefore they take on the boundary of whoever lifts them, and they may even reach a place outside the boundary; while according to those who disagree, who follow the view of Rabbi Yose ben Rabbi Nuri, ownerless objects do acquire a resting place where they are, and the barrel does not travel further than the feet of its owner.