Deuteronomy 17:6; Deuteronomy 19:15

qOn the evidence of two witnesses or of three witnesses the one who is to die shall be put to death; a person shall not be put to death on the evidence of one witness.


Laws Concerning Witnesses

15 A single witness shall not suffice against a person for any crime or for any wrong in connection with any offense that he has committed. bOnly on the evidence of two witnesses or of three witnesses shall a charge be established.