(Beraisa): If Nochrim came to cities close to the border to take from them even straw and even wood, we go out against them with weapons, and return the weapons to their places;

If they came to cities enveloped [without Eretz Yisrael, and not close to the border], we do not go out against them with weapons, unless they come for mortal issues.

Originally, [after defeating the enemy] they used to bring the weapon to the house close to the wall (outside the wall, to avoid Hachnasah to Reshus ha'Yachid). Once, the enemy [saw this, and] came upon them. [The Yisraelim rushed to the house in which the weapons were stored, and] were pushing to take the weapons. They killed each other more than the enemy killed! They enacted then that everyone takes [his weapon back] to his house.

(Mishnah - R. Meir): If one stopped on the road and got up [after dark] and found that he is within the Techum of a city, he may not enter it, for he did not intend for this;

R. Yehudah says, he may enter;

R. Yehudah: A case occurred in which R. Tarfon entered, even though he did not intend for this beforehand.

(Gemara) Question: [Chachamim] said [to R. Yehudah, what is your proof from R. Tarfon]? R. Tarfon's Beis Midrash was within 2000 Amos. Perhaps he acquired himself to Bnei Iro (i.e. the Shevisah of people of his city) during the day (before Shabbos)!

Answer: A Beraisa was found teaching that in the morning, the sun shone. They said to him "Rebbi, the city is in front of you - enter!'' (This shows that that he did not know that he is close to the city.)