Vindicate me, Lord,
    for I have led a blameless life;
I have trusted in the Lord
    and have not faltered.
Test me, Lord, and try me,
    examine my heart and my mind;
for I have always been mindful of your unfailing love
    and have lived in reliance on your faithfulness.

David was asking God to declare him innocent. He was not claiming to be sinless. He was pleading with God to clear his name. False charges were being placed against him by his enemies. David was also asking God to examine his heart and motives. He trusted God to forgive him and clear his record according to his mercy. Are you having to deal with false accusations coming your way? Are you trying to defend yourself? Take your concerns to God and have him examine your heart and motives. If you have done something wrong, ask for forgiveness and work to make things right. If you have not done anything, and you are blameless; stay steadfast and ask God to work in your life to clear your record.