Numbers 35:32

ולא תקחו כפר לנוס אל עיר מקלטו AND YE SHALL TAKE NO RANSOM לנוס TO HIS CITY OF REFUGE — The last words are the same as לַנָּס אל עיר מקלטו, "ye shall take no ransom for one who is fled to a city of refuge, i.e., one who has killed inadvertently, cannot be freed from exile by money, by giving a ransom (Sifrei Bamidbar 160:12), לשוב לשבת בארץ THAT HE SHOULD RETURN TO DWELL IN THE LAND before the High Priest dies. לנוס (the passive participle) has the same meaning as לַנָּס (the active participle), just as, (Micha 2:8) "שובי מלחמה”, which means “those who have returned from battle”; and so, too, (Zephaniah 3:18) “those who are removed far (נוני) from the appointed season”; (Joshua 5:5): “for they were circumcised men (מולים)”. Now just as you say שוב in reference to one who has already returned, and מול in reference to one who is already circumcised, so you can say לנוס in reference to one who has already fled. It calls him נוס (the passive participle), as much as to say “one who was made to flee”; — But you say that לנוס means “to flee” (the infinitive) explaining it thus: “ye shall take no ransom for one who ought to flee”, in order to free him from exile (cf. Sifrei Bamidbar 160:12), then I do not know how it can be said: “ye shall take no ransom … so that he should return to dwell in the land”, for you see, he has not yet fled, so from where shall he return?

וְלֹא־תִקְח֣וּ כֹ֔פֶר לָנ֖וּס אֶל־עִ֣יר מִקְלָט֑וֹ לָשׁוּב֙ לָשֶׁ֣בֶת בָּאָ֔רֶץ עַד־מ֖וֹת הַכֹּהֵֽן׃

And you shall take no ransom for him that is fled to the city of his refuge, that he should come back to dwell in the land, until the death of the priest.