For they being ignorant of God's righteousness, and going about to establish their own righteousness, have not submitted themselves unto the righteousness of God.
Paul, in Romans 10:3
When you walk in the Spirit of Christ, you cannot believe a lie because the Spirit of Christ will not allow a lie to enter into your heart. Nobody could lie to Jesus because he walked in the Spirit, and he suffered and died so that we might also walk in it.
As a young man, after he was converted, my father was boasting one day to an elderly mother in Christ of his new way of living. The wise old saint listened patiently as the young convert told of how he used to tell lies, but did no more. Then she replied, “Oh, Brother Clark, there’s something better than not telling lies.”
“Not believing them..”
That mother in Christ was actually reproving my father for boasting in his righteousness rather than rejoicing in God’s. What we can do within our own strength and will is our righteousness; what we can only do by the power of God is His righteousness. We can make up our own minds to tell no lie, but no amount of will-power can save us from believing a lie. Only God’s power living within us can do that.
Paul said, “If any man boast, let it be in the Lord.” That means, if we are going to boast about being good, let it be a boast of the kind of goodness that only God can create in us. Sinners can make up their minds not to commit adultery, but they cannot purify their hearts from wicked lusts. They can, with their own will-power, decide not to murder, but they cannot fill their hearts with the love of God for others.
Christ came to make God’s righteousness available to us, through the Spirit. This is another reason why, without the Spirit, no man can please God and be saved in the end, or even belong to God’s family.