Deuteronomy 17:6 New King James Version (NKJV)

⁶ Whoever is deserving of death shall be put to death on the testimony of two or three witnesses; he shall not be put to death on the testimony of one witness.

Deuteronomy 19:15 New King James Version (NKJV)

The Law Concerning Witnesses

¹⁵ “One witness shall not rise against a man concerning any iniquity or any sin that he commits; by the mouth of two or three witnesses the matter shall be established.

Matthew 18:16 New King James Version (NKJV)

¹⁶ But if he will not hear, take with you one or two more, that ‘by the mouth of two or three witnesses every word may be established.’