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.