Matthew Henry on Deuteronomy 19:15-21

Sentence should never be passed upon the testimony of one witness alone. A false witness should suffer the same punishment which he sought to have inflicted upon the person he accused. Nor could any law be more just. Let all Christians not only be cautious in bearing witness in public, but be careful not to join in private slanders; and let all whose consciences accuse them of crime, without delay flee for refuge to the hope set before them in Jesus Christ.