שולחן ערוך אורח חיים · סימן ת״ז

English

One who went out of the Shabbat barrier with permission, for example a midwife brought a child or things like that, she has two thousand amot in each direction from that spot that he arrived at; and if he arrived to a city, then he is like the people of the city and he has two thousand [amot] in each direction outside the city (look at the end of Siman 248.)

English

If he goes out with permission and walks on the path, and they said to him: the mitzvah is already made when you went out to do [it], he has from his place two thousand amot in each direction; if he has a little of the barrier that he went out from with permission, it is absorbed within the two thousand amot that he has from his place, when he returns to his place it is like he didn't go out.

English

All those who venture forth to rescue from the hands of non-Jews, or from the river, or from the rubble – have two thousand cubits in each direction from the place of rescue; and if the hand of the non-Jews was powerful, and [the rescuers] were afraid to remain in the place of rescue, they may return on Shabbat to their own location, with their weapons.