Deuteronomy 19 6
Otherwise the avenger in his anger might chase after the man and catch up with him and kill him, if it's a long distance. The man would be killed even though he didn't deserve to die, because he hadn't meant to cause any harm.
Compare with other 3 random translations
NKJ Deuteronomy 19:6lest the avenger of blood, while his anger is hot, pursue the manslayer and overtake him, because the way is long, and kill him, though he was not deserving of death, since he had not hated the victim in time past.
NLT Deuteronomy 19:6“If the distance to the nearest city of refuge is too far, an enraged avenger might be able to chase down and kill the person who caused the death. Then the slayer would die unfairly, since he had never shown hostility toward the person who died.
ASV Deuteronomy 19:6lest the avenger of blood pursue the manslayer, while his heart is hot, and overtake him, because the way is long, and smite him mortally; whereas he was not worthy of death, inasmuch as he hated him not in time past.