Have mercy upon me. Psalm 51 tells of David's repentance, confession and plea for cleansing following Nathan's rebuke after his sin with respect to Bathsheba and Uriah (2 Samuel 12:1-15). Psalm 32 tells of his joy after God forgave him (Psalm 51:12).

have I sinned. There is no sin that injures only the sinner, and/or those he has wronged, for all sin is against God's holy purpose for one's life. David had certainly sinned against both Bathsheba and Uriah, but it was even a greater sin against God. This sin had “given great occasion to the enemies of the Lord to blaspheme” (2 Samuel 12:14).

conceive. There is no sin in the act of conception itself when carried out in the bond of marriage (Hebrews 13:4). This testimony refers rather to “original sin,” the sin-nature inherited from Adam and Eve.

hyssop. Hyssop was a small shrub used to sprinkle blood and water over the cleansed leper, symbolizing his purification and cleansing (Leviticus 14:4-7).

Create in me. Only God can create, including the great miracle of regeneration, which is truly a “new creation” (2 Corinthians 5:17).

thy holy spirit. Since the death and resurrection of Christ, He has promised that the Holy Spirit will indwell His believing disciples forever (John 14:16-17). Before Christ, the Holy Spirit would come upon individuals for specific empowerment for service and could as easily leave, as in the case of Saul (1 Samuel 11:6; 16:14). David earnestly prayed that this would not happen also to him.

Restore unto me. Once a believer has truly been saved, either before or after Christ, he can never become unsaved (John 10:28; Romans 8:35; etc.). However, through overt sin, a believer may lose the joy of his salvation.