Makkos, Chapter 2, Mishnah 6. This mishnah deals with the process that every killer goes through in relation to the city of refuge: from the initial flight until his return home.
The beginning of the process - hurrying to a city of refuge:
Rabbi Yosi bar Yehudah says: "Batechilah, echad shogeg ve'echad meizid makdimin le'ir miklat" - whether he killed unintentionally or intentionally, the killer hurries and flees to the city of refuge. This is implied by the verse stated regarding one who kills intentionally: "And if a man hates his fellow and lies in wait for him and rises up against him and strikes him mortally... and he flees to one of these cities" - even one who lies in wait for his fellow and kills him flees to one of these cities.
"U'veis din sholchin u'mevi'in oso mi'sham" - the court sends and brings him from the city of refuge in order to determine his judgment, and from here there are three possibilities:
"Mi shenischayev misah b'veis din - haraguhu" - one who was found liable to death was put to death.
"V'shelo nischayev misah - petaruhu" - one who was not found liable to death was set free.
"U'mi shenischayev galus - machzirin oso limkomo" - if it was determined that he killed unintentionally and his sentence is exile, he is returned to his original place, to the city of refuge to which he fled in the first place, as it says: "And the congregation shall return him to his city of refuge" - "the congregation" means the court, for they are the ones who return him to the city of refuge.
Who counts as a 'Kohen Gadol' regarding leaving the exile?
One who killed unintentionally remains in the city of refuge until the death of the Kohen Gadol. Which Kohen Gadol counts for this purpose? The mishnah lists three:
"Echad hamashuach b'shemen hamishchah" - a Kohen Gadol who was appointed through anointing with the anointing oil, which was the practice only in the first Beis HaMikdash.
"V'echad hamerubeh begadim" - a Kohen Gadol who became Kohen Gadol by virtue of wearing the eight garments that a Kohen Gadol wears, as opposed to the four garments of an ordinary kohen. This was the case in the second Beis HaMikdash.
"V'echad she'avar mi'meshichaso" - one who was anointed as Kohen Gadol and afterward left his position: for example, the Kohen Gadol was unavailable and another was appointed in his place, and when the original Kohen Gadol returned to his position, the other one left his post.
All three of them count as a Kohen Gadol for this purpose: upon their death the killer may leave his place of exile and return home, and the blood avenger may no longer kill him.
"Rabbi Yehudah omer: af meshuach milchamah machzir es haro'tze'ach" - the meshuach milchamah is a special kohen who was anointed to speak to the people before they went out to war, and his death too returns the killer to his home. The basis of the dispute lies in the number of times the term "Kohen Gadol" appears in the passage, which is three times. Rabbi Yehudah holds that the place where it says "after the death of the kohen" also refers to the Kohen Gadol and is counted along with them, and from here there is an extra mention that includes the meshuach milchamah. And the Sages say: since the word "Gadol" is not stated there, it is not counted, and therefore there is no additional word to include the meshuach milchamah.
The mothers of the Kohanim Gedolim:
Since it is the death of the Kohen Gadol that permits the killer to leave his exile, the mothers of the kohanim - apparently the mothers of the Kohanim Gedolim - would supply food and clothing to those living in the cities of refuge, so that they would not pray that their sons die. The concern was that one sitting in the city of refuge and waiting for the death of the Kohen Gadol would pray for his death; therefore they made his life there easier, and since his life is comfortable, he may well have more interest in staying.
The death of the Kohen Gadol at different stages:
The murderer's verdict of exile was already handed down, and before he left, the Kohen Gadol died - he does not need to go into exile at all, since he has already received the atonement that the death of the Kohen Gadol provides.
The Kohen Gadol died before the verdict was handed down and another Kohen Gadol was appointed in his place, and after this second appointment the murderer was sentenced to exile - he must wait until the second Kohen dies, and only then may he return home.
Here a question arises. Our Sages taught us that the death of the Kohen Gadol is the dividing line for the murderer's return, because it was the Kohen Gadol's duty to pray that no cases of accidental killing occur in his generation, and therefore a certain measure of blame rests upon him. If so, in the second case, what blame is there on this Kohen Gadol, seeing that the killing took place before he was appointed? The Gemara answers: it was his duty to pray that his generation be such that this murderer would not need to go into exile, and since he did not achieve that, a certain measure of blame rests upon him.
In summary: In this Mishnah we learned the course the murderer follows, from his initial flight to the city of refuge, through his being brought to beis din and the division of the ruling into three - death, exemption and exile - until his return home upon the death of the Kohen Gadol. We examined the three types of Kohen Gadol whose death allows the murderer to return, the dispute between Rabbi Yehudah and the Sages regarding the kohen anointed for war, the actions of the mothers of the Kohanim Gedolim, and the law concerning the death of the Kohen Gadol before the verdict and after it.