The Ninth Commandment reads, “You shall not bear false witness against your neighbour” (Exodus 20:16). This commandment is often paraphrased simply as, “You shall not lie.” This is not strictly accurate, as it refers to lying in a legal setting (often called perjury) rather than general cases of lying. This doesn’t mean lying isn’t a serious sin in God’s eyes; we shall see that it is. However, the Ten Commandments were part of a human legal system, and (like modern criminal codes) set down perjury as a crime because this kind of lie has particularly serious consequences.
The Law of Moses expanded in other places on this commandment. Exodus 23:1-3, 6-7 states that false witness is equally wrong whether it is used to clear the guilty or frame the innocent. Leviticus 5:1 specifies that refraining from testifying when called to do so is just as bad as giving false witness. Deuteronomy 19:16-21 gives the penalty for false witness: whatever penalty the wrongfully accused would have received is pronounced upon the false witness.
As far as I am aware, there is only one place in the Law of Moses where lying is forbidden in a general way: “You shall not steal; you shall not deal falsely; you shall not lie to one another” (Leviticus 19:11). This seems to be an elaboration of the Eighth Commandment rather than the Ninth (and shows the close relationship between stealing and deceit). However, a survey of the rest of the Old Testament reveals that God condemns false witness and lying in equally strong language.
In Proverbs 6:16-19, both “a lying tongue” and “a false witness who breathes out lies” are listed among the proverbial seven things that the Lord hates. The Psalms are replete with condemnation of liars. Perhaps the starkest of these passages is Psalm 101:7, in which the Lord decrees, “No one who practices deceit shall dwell in my house; no one who utters lies shall continue before my eyes.” The Psalms also declare God’s pleasure in those who speak truth in their hearts (Psalm 15:2-3; 51:6). God Himself does not lie; indeed this is an impossibility (Numbers 23:19; Titus 1:2; Hebrews 6:18).
As we come to the New Testament, it might be a surprise to some that the verb ‘to lie’ is never spoken by Jesus in the Gospels (at least in most literal translations). However, he did have plenty to say about false witness, including an endorsement of the Ninth Commandment (Matthew 15:19; 19:18; Mark 10:19; Luke 18:20). Jesus himself was accused of false witness (John 8:13), and was the target of false witness in his trial (Mark 14:56-59).
Besides this, there are two sayings of Jesus which bring lying to the fore of our understanding of the Ninth Commandment. One is in the Antitheses of Matthew 5, already quoted in our discussions of the Sixth and Seventh Commandments. In Matthew 5:33-37 Jesus commands his followers not take oaths; instead, “Let what you say be simply ‘Yes’ or ‘No’; anything more than this comes from evil” (v. 37). Here, Jesus removes any distinction between the formal legal setting and the everyday setting. A lie is a lie, and dressing a statement up with solemn oaths if anything makes it more suspect!
Jesus’ other major saying about lying is found in his indictment of the devil in John 8:44: “You are of your father the devil, and your will is to do your father’s desires. He was a murderer from the beginning, and has nothing to do with the truth, because there is no truth in him. When he lies, he speaks out of his own character, for he is a liar and the father of lies.” This almost certainly includes an allusion to the serpent of Eden, and reminds us that it was a lie that led to the original sin (Genesis 3:4, 13). To call the archenemy of God “the father of lies” shows that lying is at the heart of what sin is, just as truth is at the heart of who God is. The Greek word diabolos (from which we get ‘devil’) means false accuser, so the devil is in fact named after his tendency to break the Ninth Commandment.
In all our discussion we have not defined what lying actually is. My definition of lying is an attempt to disguise or distort reality. When we try to mislead others, whether through something we say, or do not say, or even through body language or our tone of voice, we lie. With this definition in mind, can any of us go even one day without lying?
At a personal level, I have to bear in mind that my own area of expertise (statistics) has very often been used to disguise rather than expose reality. A famous saying popularized by Mark Twain over 100 years ago states that there are three kinds of lies: lies, damned lies, and statistics. Even our most sophisticated methods for establishing truth are often misused in order to obscure it. The prophet Jeremiah well said that the heart is deceitful above all things (Jeremiah 17:9)!