[If] one throws a stone into a public domain and kills, he is exiled. R' Eliezer ben Yaakov says: If, after the stone left his hand, the other one put his head out and received the blow, he is exempt. [If] he threw a stone into his own yard and killed —- if the victim had a right to enter there, he is exiled, but if not, he is not exiled; as it is said (Deut. 19:5): And whoever comes with his fellowman into the forest —- [it must be] like the forest, which is a place into which [both] the victim and the assailant have permission to enter. This excludes the courtyard of the householder, into which the victim and the assailant may not [both] enter. Abba Shaul says: [It must be] like chopping wood, [which is] an optional act. This excludes the father who hits his son, and the teacher who chastises his pupil, and the agent of the court.

A father is exiled as a result of his son, and a son is exiled as a result of his father. All are exiled as a result of an Israelite, and Israelites are exiled as a result of them, with the exception of a resident alien. A resident alien is exiled only as a result of a resident alien.  A blind person is not exiled; [these are] the words of R' Yehudah. R' Meir [however] says: He is exiled.  An enemy is not exiled. R' Yose bar Yehudah says: An enemy is executed because he is considered forewarned. R' Shimon says: Some enemies are exiled and some enemies are not exiled. This is the rule: Anyone concerning whom it can be said [that] he killed intentionally is not exiled; but [if it is clear] that he killed unintentionally, he is exiled.

Where are they exiled? To the cities of refuge: to the three on the other side of the Jordan, and to the three in the land of Ca-naan, as it is said (Num. 35:14): Three of the cities you shall place on the other side of the Jordan, and three of the cities you shall place in the land of Canaan, etc. As long as the three in Eretz Yisrael were not yet chosen, the three on the other side of the Jordan did not afford refuge, as it is said (Num. 35:13): There shall be six cities of refuge —- until all six of them afford refuge simultaneously.

Direct roads were laid out from one to another, as it is said (Deut. 19:3): Prepare the way for yourself, and divide into three parts, etc. They would appoint for them two Torah scholars so that he should not kill him on the way, and they would speak to him. R' Meir says: He, too, should speak for himself, as it is said (Deut. 19:4): And this is the matter of the murderer.