Charles Ellicott Commentary Numbers 35:26

"But if the manslayer shall at any time go beyond the border of his city of refuge, whither he fleeth," — Numbers 35:26 (ASV)

But if the slayer shall at any time come without the border of the city ... — As the bodily safety of the Israelite who had slain a man depended on his strict observance of the law that required him to remain within the city of refuge until the death of the high priest, so in the same way the spiritual safety of the believer depends on his exclusive reliance on the merits and efficacy of the atoning death and righteousness of Christ, since there is none other name under heaven given among men whereby we may be saved; neither is there salvation in any other (Acts 4:12).