Psalm 18:21-23 For I have kept the ways of the Lord, and have not wickedly departed from my God. For all his judgments were before me, and I did not put away his statutes from me. I was also upright before him, and I kept myself from mine iniquity.
The Lord gloriously answered David’s prayer and delivered him. As a result of God’s power and love in answer to prayer, he keeps God’s ways and keeps himself from sin. The received salvation of God provides the desire and ability to keep His ways. Keeping His ways results in a good life, while keeping our selfish, sinful ways yields a bad life.
Jesus Christ died and rose for us in order to grant us God’s righteousness by grace as a gift. By faith we are righteous. “Abraham believed God, and it was counted to him as righteousness.” David says God rewarded him according to his righteousness (v. 20). We are not righteous by our own works, but we are righteous by the faith worked in us by the Spirit through the Gospel. I am the righteous one who lives by faith, for the gospel is the power of God. By faith in Christ I keep His ways.