According to Imam, the teaching of the Book and Wisdom will be impossible unless purgation comes first. You should purge your 'selves' from all contaminations.
The worst one is the contamination of the 'self' with selfish and animal desires.
Those who are trying to train others in this world should first purge themselves.
Those who seek to rule over human beings should be purged and purified if they do not want to rebel (against God) and to not commit satanic deeds; The Ordainment is for this purpose.