Integrity means that your life is whole, that your heart is not divided. Jesus said, "No one can serve two masters" (Matthew 6:24). That's integrity. "Duplicity" means trying to serve two masters. Our Lord also said that nobody can look in two directions at the same time. If your eye is single, then your body is full of light. But if your eye is double, watch out. The darkness is coming in (Matthew 6:22-23). If you look at the darkness and the light simultaneously, the darkness crowds out the light.
In Psalm 25:21 David prayed, "Let integrity and uprightness preserve me, for I wait for You"; and in the first verse of today' passage, "Vindicate me, O Lord, for I have walked in my integrity." When we do business with or are ministering to someone, we want that person to have integrity.
When we have integrity, David tells us, we don't have to be afraid of sliding. "I have walked in my integrity. I have also trusted in the Lord; I shall not slip" (v. 1). He also says, "My foot stands in an even place" (v. 12). The word "even" means "a level place." David says, "I'm on the level because I have integrity. I have nothing in my heart against the Lord. I am not disobeying Him."
We also need not be afraid of testing. David writes, "Examine me, O Lord, and prove me; try my mind and my heart" (v. 2). He says, in other words, "Lord, I can go through the furnace. I can go through the X-ray. Go ahead and test me. I'm not afraid." When your life is whole before God and others, when you're practicing integrity, when you have a good conscience, you don't have to be afraid of the battle or the furnace or the X-ray or the testing. God will see you through.
When you walk with integrity, you walk on solid ground. Never try to serve two masters. Always keep your heart undivided before the Lord.
~Warren W. Wiersbe~