976. Making an Eiruv With One's Feet
Eiruvin 7:1
Let’s say that someone left the city on Friday and stood in a certain spot within the Shabbos boundary or at the end of Shabbos boundary and verbalized that this was his designated place for Shabbos. Even if he returns to his city and sleeps there, the next day he is permitted to walk 2,000 cubits (about 3,500 feet) in every direction from that spot. The main means of making eiruvei techumin is to actually travel to the desired spot. The Sages instituted the alternative of making an eiruv by depositing enough food for two meals in the place without having to go and stand there in order to streamline the process. Those who could afford to do so would not have to travel and wait; rather, they could send food with an agent to deposit on their behalf.
Eiruvin 7:2
Similarly, if a person wants to designate his place for Shabbos in a particular location, such as by a certain tree, house, or fence that he can identify and, at nightfall, there are 2,000 cubits or fewer between him and that place and he is on his way to establish that place as his Shabbos base, then the next day, he may proceed to that location and continue 2,000 cubits from there in any direction. This is so even though he didn’t actually reach that place or stand there, such as if a friend diverted him to spend the night at the friend’s home, or even if he simply decided to turn back or was prevented by circumstances beyond his control. Since he decided to make that place his Shabbos base and he set out to accomplish that goal, it is considered as if he stood there or placed an eiruv there.