(Ibid. 11) "And if a man hate his neighbor, and he lie in wait for him, and he rise up against him": From here they taught: If a man transgressed a "light" commandment, in the end he will transgress a grave one. If he transgressed "You shall love your neighbor as yourself," he is destined to transgress "You shall not hate," "You shall not take revenge," "You shall not bear a grudge," and, in the end, "and your brother shall live with you" — until he arrives at the spilling of blood.
(Devarim 19:11) "and he rise up against him, etc." (Ibid. 12) "Then the elders of his city shall send, and they shall take him from there": From here R. Yossi b. Yehudah says: If one slays a soul, whether unwittingly or wittingly — all proceed to the cities of refuge, and beth-din send and bring him from there.