"Let integrity and uprightness preserve me; for I wait on thee" (Psalm 25:21).
Some have said that integrity can be measured by what a person does when no one else is looking. While this may be an indicator of integrity, it is not the real litmus test. According to Scripture, the true gauge of a man's integrity is his heart.
The world evaluates a person's integrity from what it sees in man's outward behavior. God judges integrity from what He sees in a man's heart, for "Every way of a man is right in his own eyes: but the Lord pondereth the hearts" (Proverbs 21:2). In other words, man measures integrity from the outside, and God measures integrity from the inside.
David understood that God "is a discerner of the thoughts and intents of the heart" (Hebrews 4:12) when he prayed "Search me, O God, and know my heart: try me, and know my thoughts" (Psalm 139:23). It was only through David's total inward submission that he could walk "in integrity of heart, and in uprightness" (I Kings 9:4).
It is important to understand that Biblical integrity is not reached by following a moral standard, it is through following Jesus Christ, the Author of moral standards. Being "followers of God" (Ephesians 5:1) means that we have been "crucified with Christ" (Galatians 2:20) and Christ lives in us where we can truly "walk in newness of life" (Romans 6:4).
Biblical integrity is essentially righteousness, and righteousness is impossible apart from God. Our Lord instructs us to seek "first the kingdom of God, and His righteousness" (Matthew 6:33). We are not to go about trying to establish our own righteousness, but rather to submit ourselves "unto the righteousness of God" (Romans 10:3). "For we are His workmanship, created in Christ Jesus unto good works, which God hath before ordained that we should walk in them" (Ephesians 2:10).