What is real unity?
The unity which is productive of unlimited results is first a unity of mankind which recognizes that all are sheltered beneath the overshadowing glory of the All-Glorious, that all are servants of one God; for all breathe the same atmosphere, live upon the same earth, move beneath the same heavens, receive effulgence from the same sun and are under the protection of one God. This is the most great unity, and its results are lasting if humanity adheres to it; but mankind has hitherto violated it, adhering to sectarian or other limited unities such as racial, patriotic or unity of self-interests; therefore, no great results have been forthcoming. Nevertheless, it is certain that the radiance and favors of God are encompassing, minds have developed, perceptions have become acute, sciences and arts are widespread, and capacity exists for the proclamation and promulgation of the real and ultimate unity of mankind, which will bring forth marvelous results. It will reconcile all religions, make warring nations loving, cause hostile kings to become friendly and bring peace and happiness to the human world. It will cement together the Orient and Occident, remove forever the foundations of war and upraise the ensign of the Most Great Peace. These limited unities are, therefore, signs of that great unity which will make all the human family one by being productive of the attractions of conscience in mankind.
Another unity is the spiritual unity which emanates from the breaths of the Holy Spirit. This is greater than the unity of mankind. Human unity or solidarity may be likened to the body, whereas unity from the breaths of the Holy Spirit is the spirit animating the body. This is a perfect unity. It creates such a condition in mankind that each one will make sacrifices for the other, and the utmost desire will be to forfeit life and all that pertains to it in behalf of another's good. . . .
(Abdu'l-Baha, The Promulgation of Universal Peace, p. 191)
Should any one object that, since the communities and nations and races and peoples of the world have different formalities, customs, tastes, temperaments, morals, varied thoughts, minds and opinions, it is therefore impossible for ideal unity to be made manifest and complete union among men to be realized, we say that differences are of two kinds: One leads to destruction, and that is like the difference between warring peoples and competing nations who destroy one another, uproot each other's families, do away with rest and comfort and engage in bloodshed and rapacity. That is blameworthy. But the other difference consists in variation. This is perfection itself and the cause of the appearance of Divine bounty. Consider the flowers of the rose garden. Although they are of different kinds, various colours and diverse forms and appearances, yet as they drink from one water, are swayed by one breeze and grow by the warmth and light of one sun, this variation and this difference cause each to enhance the beauty and splendour of the others. The differences in manners, in customs, in habits, in thoughts, opinions and in temperaments is the cause of the adornment of the world of mankind. This is praiseworthy. Likewise this difference and this variation, like the difference and variation of the parts and members of the human body, are the cause of the appearance of beauty and perfection. As these different parts and members are under the control of the dominant spirit, and the spirit permeates all the organs and members and rules all the arteries and veins, this difference and this variation strengthen love and harmony and this multiplicity is the greatest aid to unity. If in a garden the flowers and fragrant herbs, the blossoms and fruits, the leaves, branches and trees are of one kind, of one form, of one colour and one arrangement, there is no beauty or sweetness, but when there is variety in the world of oneness, they will appear and be displayed in the most perfect glory, beauty, exaltation and perfection. Today nothing but the power of the Word of God which encompasses the realities of things can bring the thoughts, the minds, the hearts and the spirits under the shade of one Tree. He is the potent in all things, the vivifier of souls, the preserver and the controller of the world of mankind. Praise be to God, in this day the light of the Word of God has shone forth upon all regions, and from all sects, communities, nations, tribes, peoples, religions and denominations, souls have gathered under the shadow of the Word of Oneness and have in the most intimate fellowship united and harmonized!
(Abdu'l-Baha, Tablet to the Hague, p. 13)
Above is just a very small selection from the writings of the Bahá’í Faith. For more, please visit:
https://www.bahai.org/library/authoritative-texts/prayers/bahai-prayers/