EXTRACTS FROM THE WRITINGS OF BAHÁ’U’LLÁH:
This is the Day in which God’s most excellent favours have been poured out upon men, the Day in which His most mighty grace hath been infused into all created things. It is incumbent upon all the peoples of the world to reconcile their differences, and, with perfect unity and peace, abide beneath the shadow of the Tree of His care and loving-kindness. It behoveth them to cleave to whatsoever will, in this Day, be conducive to the exaltation of their stations, and to the promotion of their best interests....
(“Gleanings from the Writings of Bahá’u’lláh”, rev. ed. (Wilmette: Bahá’í Publishing Trust, 1983), p. 6) 
God’s purpose in sending His Prophets unto men is twofold. The first is to liberate the children of men from the darkness of ignorance, and guide them to the light of true understanding. The second is to ensure the peace and tranquillity of mankind, and provide all the means by which they can be established.
(“Gleanings from the Writings of Bahá’u’lláh”, pp. 79-80) 
O ye that dwell on earth! The distinguishing feature that marketh the preeminent character of this Supreme Revelation consisteth in that We have ... laid down the essential prerequisites of concord, of understanding, of complete and enduring unity. Well is it with them that keep My statutes.
The Great Being, wishing to reveal the prerequisites of the peace and tranquillity of the world and the advancement of its peoples, hath written: The time must come when the imperative necessity for the holding of a vast, an all-embracing assemblage of men will be universally realized. The rulers and kings of the earth must needs attend it, and, participating in its deliberations, must consider such ways and means as will lay the foundations of the world’s Great Peace amongst men. Such a peace demandeth that the Great Powers should resolve, for the sake of the tranquillity of the peoples of the earth, to be fully reconciled among themselves. Should any king take up arms against another, all should unitedly arise and prevent him. If this be done, the nations of the world will no longer require any armaments, except for the purpose of preserving the security of their realms and of maintaining internal order within their territories. This will ensure the peace and composure of every people, government and nation. We fain would hope that the kings and rulers of the earth, the mirrors of the gracious and almighty name of God, may attain unto this station, and shield mankind from the onslaught of tyranny.… The day is approaching when all the peoples of the world will have adopted one universal language and one common script. When this is achieved, to whatsoever city a man may journey, it shall be as if he were entering his own home. These things are obligatory and absolutely essential. It is incumbent upon every man of insight and understanding to strive to translate that which hath been written into reality and action.... That one indeed is a man who, today, dedicateth himself to the service of the entire human race. The Great Being saith: Blessed and happy is he that ariseth to promote the best interests of the peoples and kindreds of the earth. In another passage He hath proclaimed: It is not for him to pride himself who loveth his own country, but rather for him who loveth the whole world. The earth is but one country, and mankind its citizens.
(“Gleanings from the Writings of Bahá’u’lláh”, pp. 249-250) 
O ye rulers of the earth! Wherefore have ye clouded the radiance of the Sun, and caused it to cease from shining? Hearken unto the counsel given you by the Pen of the Most High, that haply both ye and the poor may attain unto tranquillity and peace. We beseech God to assist the kings of the earth to establish peace on earth. He, verily, doth what He willeth.
O kings of the earth! We see you increasing every year your expenditures, and laying the burden thereof on your subjects. This, verily, is wholly and grossly unjust. Fear the sighs and tears of this Wronged One, and lay not excessive burdens on your peoples. Do not rob them to rear palaces for yourselves; nay rather choose for them that which ye choose for yourselves. Thus We unfold to your eyes that which profiteth you, if ye but perceive. Your people are your treasures. Beware lest your rule violate the commandments of God, and ye deliver your wards to the hands of the robber. By them ye rule, by their means ye subsist, by their aid ye conquer. Yet, how disdainfully ye look upon them! How strange, how very strange!
Now that ye have refused the Most Great Peace, hold ye fast unto this, the Lesser Peace, that haply ye may in some degree better your own condition and that of your dependents.
O rulers of the earth! Be reconciled among yourselves, that ye may need no more armaments save in a measure to safeguard your territories and dominions. Beware lest ye disregard the counsel of the All-Knowing, the Faithful.
Be united, O kings of the earth, for thereby will the tempest of discord be stilled amongst you, and your peoples find rest, if ye be of them that comprehend. Should any one among you take up arms against another, rise ye all against him, for this is naught but manifest justice.
(“Gleanings from the Writings of Bahá’u’lláh”, pp. 253-254) 
The well-being of mankind, its peace and security, are unattainable unless and until its unity is firmly established. This unity can never be achieved so long as the counsels which the Pen of the Most High hath revealed are suffered to pass unheeded.
We pray God—exalted be His glory—and cherish the hope that He may graciously assist the manifestations of affluence and power and the daysprings of sovereignty and glory, the kings of the earth—may God aid them through His strengthening grace—to establish the Lesser Peace. This, indeed, is the greatest means for ensuring the tranquillity of the nations. It is incumbent upon the Sovereigns of the world—may God assist them—unitedly to hold fast unto this Peace, which is the chief instrument for the protection of all mankind. It is Our hope that they will arise to achieve what will be conducive to the well-being of man. It is their duty to convene an all-inclusive assembly, which either they themselves or their ministers will attend, and to enforce whatever measures are required to establish unity and concord amongst men. They must put away the weapons of war, and turn to the instruments of universal reconstruction. Should one king rise up against another, all the other kings must arise to deter him. Arms and armaments will, then, be no more needed beyond that which is necessary to ensure the internal security of their respective countries. If they attain unto this all-surpassing blessing, the people of each nation will pursue, with tranquillity and contentment, their own occupations, and the groanings and lamentations of most men would be silenced. We beseech God to aid them to do His will and pleasure. He, verily, is the Lord of the throne on high and of earth below, and the Lord of this world and of the world to come. It would be preferable and more fitting that the highly-honoured kings themselves should attend such an assembly, and proclaim their edicts. Any king who will arise and carry out this task, he, verily will, in the sight of God, become the cynosure of all kings. Happy is he, and great is his blessedness!
(“Epistle to the Son of the Wolf”, rev. ed. (Wilmette: Bahá’í Publishing Trust, 1988), pp. 30-31) 
The sixth Glad-Tidings is the establishment of the Lesser Peace, details of which have formerly been revealed from Our Most Exalted Pen. Great is the blessedness of him who upholdeth it and observeth whatsoever hath been ordained by God, the All-Knowing, the All-Wise.
(“Tablets of Bahá’u’lláh Revealed after the Kitáb-i-Aqdas”, (Wilmette: Bahá’í Publishing Trust, 1988), p. 23) 
... In all matters moderation is desirable. If a thing is carried to excess, it will prove a source of evil. Consider the civilization of the West, how it hath agitated and alarmed the peoples of the world. An infernal engine hath been devised, and hath proved so cruel a weapon of destruction that its like none hath ever witnessed or heard. The purging of such deeply-rooted and overwhelming corruptions cannot be effected unless the peoples of the world unite in pursuit of one common aim and embrace one universal faith. Incline your ears unto the Call of this Wronged One and adhere firmly to the Lesser Peace.
(“Tablets of Bahá’u’lláh revealed after the Kitáb-i-Aqdas”, p. 69) 
First:It is incumbent upon the ministers of the House of Justice to promote the Lesser Peace so that the people of the earth may be relieved from the burden of exorbitant expenditures. This matter is imperative and absolutely essential, inasmuch as hostilities and conflict lie at the root of affliction and calamity.
(“Tablets of Bahá’u’lláh revealed after the Kitáb-i-Aqdas”, p. 89) 
In the abundance of Our grace and loving-kindness We have revealed specially for the rulers and ministers of the world that which is conducive to safety and protection, tranquillity and peace; haply the children of men may rest secure from the evils of oppression. He, verily, is the Protector, the Helper, the Giver of victory. It is incumbent upon the men of God’s House of Justice to fix their gaze by day and by night upon that which hath shone forth from the Pen of Glory for the training of peoples, the upbuilding of nations, the protection of man and the safeguarding of his honour.
(“Tablets of Bahá’u’lláh revealed after the Kitáb-i-Aqdas”, p. 125) 
... They that are possessed of wealth and invested with authority and power must show the profoundest regard for religion. In truth, religion is a radiant light and an impregnable stronghold for the protection and welfare of the peoples of the world, for the fear of God impelleth man to hold fast to that which is good, and shun all evil. Should the lamp of religion be obscured, chaos and confusion will ensue, and the lights of fairness and justice, of tranquillity and peace cease to shine. Unto this will bear witness every man of true understanding.
(“Tablets of Bahá’u’lláh revealed after the Kitáb-i-Aqdas”, p. 125) 
We have enjoined upon all mankind to establish the Most Great Peace—the surest of all means for the protection of humanity. The sovereigns of the world should, with one accord, hold fast thereunto, for this is the supreme instrument that can ensure the security and welfare of all peoples and nations. They, verily, are the manifestations of the power of God and the daysprings of His authority. We beseech the Almighty that He may graciously assist them in that which is conducive to the well-being of their subjects. A full explanation regarding this matter hath been previously set forth by the Pen of Glory; well is it with them that act accordingly.
(“Tablets of Bahá’u’lláh revealed after the Kitáb-i-Aqdas”, p. 126) 
The purpose of religion as revealed from the heaven of God’s holy Will is to establish unity and concord amongst the peoples of the world; make it not the cause of dissension and strife. The religion of God and His divine law are the most potent instruments and the surest of all means for the dawning of the light of unity amongst men. The progress of the world, the development of nations, the tranquillity of peoples, and the peace of all who dwell on earth are among the principles and ordinances of God. Religion bestoweth upon man the most precious of all gifts, offereth the cup of prosperity, imparteth eternal life, and showereth imperishable benefits upon mankind. It behoveth the chiefs and rulers of the world, and in particular the Trustees of God’s House of Justice, to endeavour to the utmost of their power to safeguard its position, promote its interests and exalt its station in the eyes of the world. In like manner it is incumbent upon them to enquire into the conditions of their subjects and to acquaint themselves with the affairs and activities of the divers communities in their dominions. We call upon the manifestations of the power of God—the sovereigns and rulers on earth—to bestir themselves and do all in their power that haply they may banish discord from this world and illumine it with the light of concord.
(“Tablets of Bahá’u’lláh revealed after the Kitáb-i-Aqdas”, pp. 129-130) 
Our hope is that the world’s religious leaders and the rulers thereof will unitedly arise for the reformation of this age and the rehabilitation of its fortunes. Let them, after meditating on its needs, take counsel together and, through anxious and full deliberation, administer to a diseased and sorely-afflicted world the remedy it requireth.
The Great Being saith: The heaven of divine wisdom is illumined with the two luminaries of consultation and compassion. Take ye counsel together in all matters, inasmuch as consultation is the lamp of guidance which leadeth the way, and is the bestower of understanding.
(“Tablets of Bahá’u’lláh revealed after the Kitáb-i-Aqdas”, p. 168) 
Take ye counsel together, and let your concern be only for that which profiteth mankind and bettereth the condition thereof.... Regard the world as the human body which, though created whole and perfect, has been afflicted, through divers causes, with grave ills and maladies. Not for one day did it rest, nay its sicknesses waxed more severe, as it fell under the treatment of unskilled physicians who have spurred on the steed of their worldly desires and have erred grievously. And if at one time, through the care of an able physician, a member of that body was healed, the rest remained afflicted as before. Thus informeth you the All-Knowing, the All-Wise.... That which the Lord hath ordained as the sovereign remedy and mightiest instrument for the healing of all the world is the union of all its peoples in one universal Cause, one common Faith. This can in no wise be achieved except through the power of a skilled, an all-powerful and inspired Physician. This verily is the truth, and all else naught but error.
Consider these days in which the Ancient Beauty, He Who is the Most Great Name, hath been sent down to regenerate and unify mankind. Behold how with drawn swords they rose against Him, and committed that which caused the Faithful Spirit to tremble. And whenever We said unto them: ‘Lo, the World Reformer is come,’ they made reply: ‘He, in truth, is one of the stirrers of mischief’....
(Extracts from the Tablet to Queen Victoria, cited in Shoghi Effendi, “The World Order of Bahá’u’lláh: Selected Letters”, rev. ed. (Wilmette: Bahá’í Publishing Trust, 1982), pp. 39-40; p. 163)