The Greek word translated "truth" is aletheia, which most closely resembles our English word "reality." It means "the manifested, unconcealed essence of a matter." A living, saving faith depends upon the premise by man that God is true in His being and character. The truth forms the basis for a person's conversion.
Consider this: There is a Personal, Living, Almighty God whose ways and laws are reality in spite of the way things may appear to our senses (II Corinthians 5:7). They are intrinsically right and true. Therefore a person who is honest, who is willing to speak the truth, who will acknowledge and submit to it when he sees it, will eventually be converted to be like God.
We are God's workmanship (Ephesians 2:10). God, as Creator, is making us kings and priests to administer and teach a way of life based upon revealed truth. Because He desires to share and perpetuate what He is with an entire Family of children bearing His characteristics, He cannot have anybody in His Family who does not embody truth as Jesus did.
"You shall not bear false witness" thus has far-reaching spiritual applications. It is not a commandment that we can carelessly ignore as being insignificant compared to other "more important" ones. The word "bear" indicates "spread", "carry", "render," and "give." At first, it seems to involve only perjury or gossip, but other Scriptures show it covers giving a false witness, example, or impression under any circumstance, including hypocrisy and self-deception. It includes the giving of testimony (verbally or by example) in any case that tends to produce injury. The ninth commandment regulates man's relationship to other men much as the third commandment does in man's relationship to God. This commandment directly involves faithfulness and loyalty in our mouth and example for God before men.