Numbers 35:30 in the World English Bible
“‘Whoever kills any person, the murderer shall be slain based on the testimony of witnesses; but one witness shall not testify alone against any person so that he dies.
Context
29 So these things shall be for a statute of judgment unto you throughout your generations in all your dwellings.
30 Whoso killeth any person, the murderer shall be put to death by the mouth of witnesses: but one witness shall not testify against any person to cause him to die.
31 Moreover ye shall take no satisfaction for the life of a murderer, which is guilty of death: but he shall be surely put to death.