Numbers 5:13; Numbers 35:30

Numbers 5:13

13 and a man has intercourse with her and it is hidden from the eyes of her husband and she is undetected, although she has defiled herself, and there is no witness against her and she has not been caught in the act,

Numbers 35:30

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