Numbers 35:30-32

Young's Literal Translation

³⁰ whoso smiteth a person, by the mouth of witnesses doth [one] slay the murderer; and one witness doth not testify against a person -- to die.

³¹ `And ye take no atonement for the life of a murderer who [is] condemned -- to die, for he is certainly put to death;

³² and ye take no atonement for him to flee unto the city of his refuge, to turn back to dwell in the land, until the death of the priest.