John Gill Commentary Deuteronomy 19:10

"that innocent blood be not shed in the midst of thy land, which Jehovah thy God giveth thee for an inheritance, and so blood be upon thee." — Deuteronomy 19:10 (ASV)

That innocent blood be not shed
As it would be if such a slayer as before described was killed by the avenger of blood, before he could get to one of these cities of refuge, or supposing that they had not been appointed, or a sufficient number of them:

which the Lord your God gives you for an inheritance ;
to be enjoyed by them and their children after them, provided they did not defile it by their sins, but observed the commands of the Lord to obey them and

so blood be upon you ;
the guilt of innocent blood crying for vengeance, as would be the case if such a man's blood was shed as before described; it seems as if the guilt would rather affect the whole land, for not having a proper provision of "asylums" for such persons, than the avenger of blood.