The Ten Commandments draw a straight line from love of God to love of neighbor. The two parties are distinguished, to be sure, but in the life of obedience they are inseparable. As Luther pointed out, to disobey any of the commandments is to disobey the first—"You shall have no other gods before me" (Ex. 20:3)—because all disobedience is essentially idolatry.
The outworking of allegiance to God in seeking the good of our neighbors is embedded in the Ten Commandments, as the first four are inextricable from the latter six. You cannot, in fact, have God above all gods and hate your neighbor. Jesus says so (1 John 4:20). And so does His brother James in his indictment of hypocrisy, writing: "With [the tongue] we bless our Lord and Father, and with it we curse people who are made in the likeness of God" (James 3:9).
Therefore, when we get to the ninth commandment—"You shall not bear false witness against your neighbor" (Ex. 20:16)—we should see in the background the preamble to all the commandments, the central truth of the universe: "I am the Lord your God" (Ex. 20:2). This central truth is the rein on the Christian's tongue. Without this rein—or bit, if you will (James 3:3)—our tongues roll loose, go crooked. If godly discipline is a way of life (Prov. 6:23), the non-discipline of the idolatrous tongue is a way of death. James continues:
The tongue is a small member, yet it boasts of great things. How great a forest is set ablaze by such a small fire! And the tongue is a fire, a world of unrighteousness. The tongue is set among our members, staining the whole body, setting on fire the entire course of life, and set on fire by hell. For every kind of beast and bird, of reptile and sea creature, can be tamed and has been tamed by mankind, but no human being can tame the tongue. It is a restless evil, full of deadly poison. (3:5–8)
James' picture of the deadly tongue is of speech run wild, corrupting everything it contacts just as a drop of poison ruins an entire vessel of water or a loose spark ignites an inferno. These are vivid pictures of the ninth commandment's "bearing false witness" because they show us the consequences of a tongue insubordinate to God.
Proverbs 4:24 says, "Put away from you crooked speech, and put devious talk far from you." What is crooked speech? It is talk that isn't straight, of course. It is bowed, off-kilter, circuitous. It does not draw the straight line from "you shall have no other gods before me" to "you shall not bear false witness against your neighbor." Crooked speech appears in the church in a variety of ways—lies, gossip, and hypocrisy, to mention a few. There are certainly more kinds of crooked speech, but these are the most common. Proverbs 4:24 reminds us that the Lord loves a straight shooter. As James writes later, "let your 'yes' be yes and your 'no' be no, so that you may not fall under condemnation" (5:12).
How do we get straightened out from this crookedness? James has already said that no human being can tame the tongue (3:8). We look to the fulfillment of the law, Jesus Christ, whose perfect record is imputed to us through trust in Him alone. His work is pressed to our tongue like a burning coal, setting us straight by setting us free—to love God and our neighbors. And since love rejoices with the truth (1 Cor. 13:6), the Holy Spirit brings the truth of the gospel from our changed hearts to our transformed minds and out to the words of our mouth.
The gospel-set mind realizes the line in the law runs the other way as well. When we bear false witness against our neighbor, we are bearing false witness about God. When we lie to or gossip about our brother, we are implicitly testifying that God is not our God, that He does not care about honesty or justice. If we claim allegiance to God but tear down our brothers, we declare God a liar.
The gospel calls us to a better way. When we orient ourselves around the finished work of Christ, we are compelled to bear true witness about God: "Look how wonderful and satisfying He is." And when we find Christ supremely valuable and fulfilling, the desire to cut our neighbor down disappears.
We bear true witness to God when we seek our neighbor's flourishing. We serve him and sacrifice for him. If he requires correction, we speak the truth in love and restore him gently, seeking not his shame or his exasperation but his building up in Christ. In the church, we appeal to the Christ held dear by our brethren, just as Paul did Peter, confronting him to his face, not muttering behind his back, and not cracking the whip of moralism but saying, "You are not in line with the gospel" (Gal. 2:14).
This is how we bear true witness for our neighbor—by bearing witness in our speech to and about him to the Truth. Gospel-laden speech positively speaks to the confidence in better things from our brethren, things pertaining to salvation (Heb. 6:9). And it testifies to Christ, who is the Truth (John 14:6).