In the next verse, he will declare his belief plainly.
8 Good and upright is the Lord;
God indeed can be trusted. He is good. He is upright. He does remember his mercy and steadfast love. By his goodness, he parts the sin from the sinner through the sacrifice of Christ and remembers it no more. The sins of our youth, those things we regret, the sins that plague our minds do not plague His mind.
He will again have compassion on us; he will tread our iniquities underfoot. You will cast all our sins into the depths of the sea.
He does not deal with us according to our sins, nor repay us according to our iniquities. 11 For as high as the heavens are above the earth, so great is his steadfast love toward those who fear him; 12 as far as the east is from the west, so far does he remove our transgressions from us.
8 Good and upright is the Lord; therefore he instructs sinners in the way.
The Lord is full of compassion, and he knows our weaknesses and frailties, even more, a million times more than we do. He is merciful, steadfast in His love, good, upright, and all His desires towards us are shaped by His nature according to His promises and not our nature and our failures. He uses our frailties and failures to bring about humility in us. He causes them to work for our good. He breaks us of pride so that he can make us, lead us, and teach us in His way.
9 He leads the humble in what is right, and teaches the humble his way.
David has displayed here the heart of a humble person. He has forsaken his own way. He does not believe that the answers to his desperate hour are in better military strategies or political alliances. He lifts up his soul to God alone, forsaking all other paths. If one is to find the paths of God, they must stop wandering down paths of their own making or the paths made by other men. To quote Jesus, He is the way (John 14:6), and the path is narrow and few there be that find it (Matthew 7:13-14).
David has meditated on the Law of God and discovered that “those who trust in the Lord are not put to shame.” It is those who are wantonly treacherous that are the ones who perish. Only the truth will do. Make him know it if he is too stubborn; lead him in it if he will go willingly. He waits for the Lord and none else. Whatever it takes, he is willing to undergo that trial. David’s appeals to God are not based on his merit, lineage, or position but on God’s nature and character as revealed in Scripture and his life experience. A man does not speak like this merely because he’s read the Law. A man speaks like this when he has discovered by faith through personal experience that God is good and upright. He has met with God, sacrificed to God, given time to God, and surrendered to God’s sovereign. He has learned that, “All the paths of the Lord are steadfast love and faithfulness, for those who keep his covenant and his testimonies.”
Here is the good news. If we believe in Christ, then all the promises are ours in Him. Praise be to God for Christ Jesus! He has kept covenant with God, fulfilled all his testimonies, and has satisfied the Father in every way. By faith, we are joined to Him through the Spirit, and all His righteousness is ours, and all our sin has been laid upon Him. Where we fail, he does not. Where we are weak, He is strong on our account. When we sin, He is our propitiation before the Father. What this means for us is that we can know what David knew except more. David lived under much darkness even as a prophet. We have the life of Christ in the Gospels, the Holy Spirit within us, the apostolic Church as a witness, and the writings of the apostles to interpret and expand upon the writings of David and all the prophets. The New Covenant is superior to the Old because we have Christ in us, “the hope of glory” (Colossians 1:27). We have Christ. He has come. We have but to humble ourselves before Him, bow our knees and proclaim our love for the risen King.