The laws surrounding the purification process of the Metsorah (leper) include the use of the hyssop plant, which is a very low growing plant reaching only a few inches off the ground. It is used to sprinkle the afflicted person and return him from his imposed isolation back into the community.
To better understand this process we look to our sages who explain that the affliction of the Metsorah is caused by a moral defect, notably his speaking ill and derogatorily about others. This destructive habit is usually motivated by a person’s own vanity and sense of false pride. A person with healthy self-esteem has no need to elevate himself by disparaging others, therefore in order to correct this defect, he must be humbled.
But why the symbolism of the lowly hyssop? Why doesn’t the priest just lecture the person on the destructive power of gossip and arrogance?
From here we can learn a powerful psychological insight that if a person tries to be humble because he is instructed to do so he is not likely to achieve anything more than a superficial humility, which is worthless.
Sincere humility can only be realized through insight, not preaching. The priest and this process provides the sufferer with a stimulus for introspection and if this does not initiate and bring about sincere introspection, preaching to him will be a waste of time.