A true witness delivereth souls (Proverbs 14:5; Proverbs 12:17). A true witness saves persons who are in danger owing to false accusation or calumny; saves lives; "saves from evils," says the Septuagint.
But a deceitful witness speaketh lies, and therewith endangers lives. Literally, He who breatheth out lies is deceit; he is a personification of fraud, dominated and informed by it; it has become his very nature.
"Falsehood is the devil's daughter, and speaks her father's tongue." Septuagint, "But a deceitful witness kindles ( ἐκκαίει) lies."