At the mouth of two witnesses, or three witnesses, shall he that is worthy of death be put to death; but at the mouth of one witness he shall not be put to death. Two witnesses - One might be deceived, or be prejudiced or malicious; therefore God required two substantial witnesses for the support of the charge.
Related Commentaries of Deuteronomy 17:6
Deuteronomy 17:6
6 At the mouth of two witnesses, or three witnesses, shall he that is worthy of death be put to death; but at the mouth of one witness he shall not be put to death.