Gemara

45b (Mishnah): The elders (who brought Eglah Arufah) say "our hands did not spill his blood, and our eyes did not see."

Question: Would we really think that the elders of Beis Din are murderers?!

Answer: They mean, had he come to us, we would not have exempted (ourselves from) him; had we seen him, we would not have abandoned him.

46b (Beraisa): They mean that had he come to us, we would not have exempted him without food, or left him without an escort.

(Beraisa - R. Meir): We force people to escort, since its reward is immeasurable - "show us the entrance and we will do Chesed with you... He showed them..."

The Chesed was that they killed the entire city, but spared him and his family. "The man went to the land of Chitim and built a city. He called it Luz."

(Beraisa): Sancheriv and Nevuchadnetzar were unable to disturb Luz. Even the angel of death may not enter! When one wants to die, he leaves the city and dies.

The man who showed the entrance saved himself and his progeny for eternity by merely pointing. All the more so, one who walks to escort people merits this!

(R. Yehoshua ben Levi): When Avraham left Mitzrayim, Pharaoh escorted him four steps. He merited to enslave Avraham's descendants for 400 years.

(Rav Yehudah): One who escorts a guest four Amos in the city ensures that the guest will not be harmed;

Ravina escorted Rava bar Yitzchak four Amos. On his way, Rava bar Yitzchak encountered (what normally would cause) damage, and was saved from it.

(Beraisa): A Rebbi escorts his Talmid to the Ibur of the city (70 Amos past the last houses. One escorts his friend to the Techum Shabbos (as far as one may go, 2000 Amos past the city). There is no limit to how far a Talmid escorts his Rebbi.

(Rav Sheshes): I.e., he escorts his Rebbi one Parsah (about four kilometers.) For one's primary Rebbi, one escorts him three Parsa'os.

Rav Kahana escorted Rav Simi from Fum Nahara until Bei Tzinisi of Bavel.

(R. Yosi bar Chanina): "In a land where Adam (a man) did not pass, and a man did not sit" teaches that a land is inhabited only if Adam (ha'Rishon) decreed so.

(R. Yochanan): If one does not escort or is not escorted, it is as if he murders. Had the people of Yericho escorted Elisha, he would not have incited bears to attack the children.

Rishonim

Rambam (Hilchos Evel 14:1,2): Escorting guests is a Mitzvas Aseh mid'Rabanan. It is Chesed with one's body, without limit. It is part of "v'Ohavta l'Re'acha Kamocha." Its reward is greatest (of all such Mitzvos).

Rambam (3): We force people to escort, just like we force to give Tzedakah. Beis Din establishes Sheluchim to escort travelers. If they were lazy, it is considered like murder. Even one who escorts four Amos in the city gets great reward. A Rebbi escorts his Talmid to the Ibur of the city. One escorts his friend to the Techum Shabbos. There is no limit to how far a Talmid escorts his Rebbi.

Keren Orah (Sotah 46b DH Tanya): Beis Din says 'we did not turn him away without an escort' because they must establish Sheluchim for this.

Likutei Halachos (Ein Mishpat 80): Whenever there is a hospitality committee, it is proper to hire someone to escort travelers and show them the roads.

Rosh (Orchos Chayim, Din Levayah): One may not return from escorting a guest as long as he can see him - "v'Eineinu Lo Ra'u."

Poskim and Acharonim

Darchei Moshe (CM 426:1): Maharash (of Neustadt, the Maharil's Rebbi) says that nowadays a Talmid does not escort his Rebbi a Parsah, for the Rebbi pardons his honor. One should escort him to the city gate, or at least four Amos.

Be'er Sheva: The Poskim did not bring the laws of escort because nowadays all the roads are dangerous, and one need not endanger himself to escort another. One's own life comes first.

Rebuttal (Iyun Yakov DH Kol and DH she'Ilmalei): In any case, the Poskim should have brought that one must escort four Amos! The Darchei Moshe and SMA say that people pardon their honor. I say that escort is so that the guest will know his way, and nowadays roads have signs so it is easy to find one's way. Therefore, four Amos suffices. Elisha did not know his way and strayed onto the youths' vineyards. This is why they told him to leave, and it led them to their death.

Ahavas Chesed (3:2, Hagahah): We can say that nowadays roads are safer and have signs to try to justify why people are not careful about escorting the Shi'urim of the Gemara. However, surely we may not exempt ourselves from a Mitzvah that protects the guest from calamity. I heard of a host whose property burned up. This is because he provided Achilah and Shtiyah (food and drink; (the initial letters spell Esh (fire), but did not finish the Mitzvah with Leviyah.

Likutei Halachos (Ein Mishpat 300): Where the roads are poor and people often err and the guest fears lest he err, how are people Yotzei with an escort of only four Amos or until the gate?!

Ha'Rif (DH Kol): Had people accompanied Elisha, they would have appeased him or rebuked the youths.

Maharal (Nesivos Olam, Gemilus Chasadim 5): The teaching that a land is inhabited only if Adam decreed so (i.e. the land corresponds to an important part of man) follows the episode in which Rav Kahana escorted Rav Simi from Fum Nahara until Bei Tzinisi. This teaches that Mazikim have power over man when he leaves a settled place, so he needs an escort. Even if he was escorted only part of the way, Mazikim have no power over him the entire way. Also, when Tzelem Elokim is in man, "u'Mora'achem v'Chitchem Yihyeh Al Kol Chayas ha'Aretz"; even Mazikim do not rule over him. If one is escorted, the honor of Tzelem Elokim remains in him. If not, it departs. This itself, Bitul of the Tzelem Elokim, is like bloodshed! Since escort causes the traveler to be guarded without limit, its reward is limitless.

Maharsha (Sotah 46b DH Kol): 'She'Eino Melaveh u'Mislaveh' connotes that also the guest is to blame! We can explain that one who does not escort is like a murderer, even if the guest is escorted, i.e. he does not need their escort, like Elisha. "V'Hu" is extra to teach that he was alone, without an escort.

Ahavas Chesed (ibid.): 'She'Eino Melaveh u'Mislaveh' teaches that the guest should not pardon the host from escorting him.