Reference for Makkot 24:9

מכאן אמרו בן לוי שהרג גולה מפלך לפלך ואם גלה לפלכו פלכו קולטו אמר רב אחא בריה דרב איקא מאי קרא (במדבר לה, כח) כי בעיר מקלטו ישב עיר שקלטתו כבר:

From here it was said, A levite that killed is exiled from district to district, but if he exiled himself to his own district, then his district protects [him]. Rav Acha brei dRav Ikka says, What is the meaning of the verse, (Numbers 35,28) "For in a city of refuge he shall dwell"? A city which previously afforded him protection.

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