The fact is, that the functions of the religious leaders and the duties of experts in religious law are to keep watch over spiritual matters and to spread abroad the virtues of the Merciful. Whenever the leaders of the manifest religion, the pillars of religious law, have sought a role in the political sphere, have issued opinions and taken control, the unity of the believers in the one true God has been dissolved, and schisms have encompassed the community of the faithful. ... Gracious God! Shall a people who are not able to manage their own little nests, or to instruct their own households, who are unaware of domestic and foreign affairs, shall these interfere in the weighty affairs of the kingdom and its subjects, and raise opposition in the complexities of political matters? If you refer to history, you would find countless examples of this sort, all based on the involvement of religious leaders in political matters. These souls are the fountainhead of the interpretation of God’s commandments, not of implementation. That is, when the government requests an explanation concerning the requirements of the Law of God and the realities of the divine ordinances, in principle or in a specific case, they must explain what they have deduced from the commands of God and what is in accordance with the law of God. Apart from this, what awareness do they have of questions of leadership and social development, the administration and control of weighty matters, the welfare and prosperity of the kingdom, the improvement of procedures and codes of law, or foreign affairs and domestic policy?
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" ...human society requires the training and cultivation of a true master, and that human souls need a governor, one who binds and restrains, prohibits and encourages, one who impels and leads. For the garden of his creation cannot attain beauty, delicacy and plenty except through the training of the kindly gardener, the overflowing bounty from the realm of unicity, and the just governance provided by the government.
Now this prohibition and prevention, rules and restraints, leading and impelling, is divided into two types. The first protector and restrainer is the power of governance that is related to the physical world, a power that guarantees happiness in the external aspects of human existence. It safeguards human life, property and honour, and the exalted quality and refined virtues of the social life of this illustrious race. Just monarchs, accomplished representatives, wise ministers, and intrepid military leaders constitute the executive centre in this power of governance, the axis of the wheel of these divine favours.
The second type of educator and governor of the human world is sacred and spiritual power: the heavenly Books that have been sent down, the prophets of God, and spiritual souls and devout religious leaders. For those in whom revelation descends and divine inspiration arises are the educators of hearts and minds, the correctors of morals. they beautify conduct and encourage the faithful."
http://www.h-net.org/~bahai/trans/vol7/govern.htm