Numbers 35:30

If anyone kills a person , the murderer shall be put to death on the evidence of witnesses . But no person shall be put to death on the testimony of one witness .

“‘Anyone who kills a person is to be put to death as a murderer only on the testimony of witnesses. But no one is to be put to death on the testimony of only one witness.

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.