TRUTH: Hyssop is mentioned throughout the Old Testament as an instrument designed by God for religious purification, according to the Law of Moses. This can be found in Exodus 12:22 and so they put a sponge full of the sour wine (vinegar) upon a branch of hyssop and brought it up to His mouth (John 12:29b). Hyssop is a plant or herb with amazing qualities, just like everything the Father designed. Apart from the potential to cleans and regulate normal hygiene and daily functions of the intestines etc, Hyssop contains qualities which can treat asthma, bronchitis, sore throats and more. A paste from it can treat bruises and small burns.
So it is with the Word of God - it soothes, heals, cleanses, corrects and purifies. It is our conscience and our guide which the Holy Spirit, Who lives alongside the spirit of each truly converted Christian, uses to guide us into the path of God's Truth. In this prayer of Repentance (Psalm 51), King David knew the depth of his sin, but he also knew the Holy Spirit would deliver him if He would apply the spiritual attributes of the Hyssop plant to his dark depressed spiritual condition. Many Christians live with hidden sins in their lives and need not salvation, but purification. The first thing required is a willingness to "halt" the bleeding and bind up that wound. Then next up is a cry out to God to apply the bitter dose of the hyssop plant of Discipline. Depending on the sin, this discipline may not go over well, but it will correct the ship of the person's state. Then, third, once that discipline has been applied to the affliction and application is made, restoration can return with sweet release, as the burdens are lifted up by Grace! So now, if a dose of spiritual hyssop is needed, why not confess to God now, and accept His Grace?