(Bamidbar 35:13) "Cities of refuge they shall be" (Sifri) I only know that they provide refuge in the land; how do I know about outside the land? Therefore, it says "they shall be".
We cannot explain this as per the simple meaning, since these cities were only set up in Eretz Yisrael. Kesef Mishneh explains either it is referring to the cities in Ever HaYardein (other side of the river), or is a case of a person from outside that Land that flees to these cities after an accidental murder.
T.T. This explanation cannot be the first (simple) explanation, because we never find Ever HaYardein referred as outside of the Land. Rambam does bring another Sifri on a latter verse אלה which explicitly limits these cities to within the Land. However, our texts do not have this Sifri. This is another example where the Rishonim have certain portions of texts, and we do not have them.
