Psalm 40, 41

One thing that continually strikes me about the Psalms is that David (and the other writers) didn't live in the time of grace post resurrection. So as in these 2 Psalms you have David making pleas to God reminding him of his salvation and promises. It is almost like, 'God you said do this and I've done it so therefore please have compassion on me.' Of course being pre resurrection they did not have the promise of forgiveness of sins as we have it. Jesus' blood had not be shed for them at that point in time.

At the same time we shouldn't shun asking God for help, for protection, for his blessings. Our battles are not against flesh and blood but against spiritual powers and strongholds. BUT we live with the assurance that Jesus the Messiah has died for our sins and we have salvation through his blood that wipes clean for us the record book of our wrongs.