If you're a parent, did you ever have to teach your child how to lie? Of course not. But you did at one point have to say, "No, sweetheart, it's wrong to tell a lie. Telling the truth is the right thing to do."
That's because even though we're created in the image of God, that image is marred because of the fall, and lying comes pretty naturally to us. But God gave us His standard in the ninth commandment: "You shall not bear false witness against your neighbor" (Exodus 20:16).
What does this commandment tell us about the Lord? Simply that we're dealing with a God who loves truth (see Exodus 34:6; Deuteronomy 32:4; Psalm 51:6). Falsehood cannot be long tolerated by someone whose essence and nature is that of truth. No wonder Solomon wrote in Proverbs 12:22, "Lying lips are an abomination to the Lord."
It follows that if God loves the truth, then His children should as well. And one of the most loving things we can do is tell other people the truth about eternity, heaven, and hell, even when it's not easy. As Paul wrote in 1 Corinthians 13, love "does not rejoice in iniquity, but rejoices in the truth" (v. 6).
Think of Jesus Christ: He was incarnate love, and He spoke the truth when it was both pleasant (see Matthew 16:17) and unpleasant (see Matthew 3:7) to do so. That's because God and His truth cannot be changed. The gospel is the gospel; it's nonnegotiable. If we take anything from the ninth commandment, it should be the fact that we're dealing with a God of truth who loves the truth.
On the flipside, did you know Satan is called the Father of Lies (see John 8:44)? This means whenever we deliberately engage in a lie, we're allying ourselves with him. It's sort of like putting your arm around him and saying, "We're partners. Let's work together."
So how are you doing when it comes to telling the truth? Jesus said, "Let your 'Yes' be 'Yes,' and your 'No,' 'No'" (Matthew 5:37). That's a perfect description of verbal integrity, of living what you say. So say what needs to be said, nothing more. And speak the truth in love, knowing that you reflect the character of the God you serve when you do so.