Among the institutes of the Holy Books is that of the foundation of places of worship. That is to say, an edifice or temple is to be built in order that humanity might find a place of meeting, and this is to be conducive to unity and fellowship among them. The real temple is the very Word of God; for to it all humanity must turn, and it is the center of unity for all mankind. It is the collective center, the cause of accord and communion of hearts, the sign of the solidarity of the human race, the source of eternal life. Temples are the symbols of the divine uniting force so that when the people gather there in the House of God they may recall the fact that the law has been revealed for them and that the law is to unite them. They will realize that just as this temple was founded for the unification of mankind, the law preceding and creating it came forth in the manifest Word. Jesus Christ, addressing Peter, said, "Thou art Peter, and upon this rock I will build my church." This utterance was indicative of the faith of Peter, signifying: This faith of thine, O Peter, is the very cause and message of unity to the nations; it shall be the bond of union between the hearts of men and the foundation of the oneness of the world of humanity.
In brief, the original purpose of temples and houses of worship is simply that of unity -- places of meeting where various peoples, different races and souls of every capacity may come together in order that love and agreement should be manifest between them. That is why Bahá'u'lláh has commanded that a place of worship be built for all the religionists of the world; that all religions, races and sects may come together within its universal shelter; that the proclamation of the oneness of mankind shall go forth from its open courts of holiness -- the announcement that humanity is the servant of God and that all are submerged in the ocean of His mercy. It is the Mashriqu'l-Adhkar. The world of existence may be likened to this temple and place of worship. For just as the external world is a place where the people of all races and colors, varying faiths, denominations and conditions come together -- just as they are submerged in the same sea of divine favors -- so, likewise, all may meet under the dome of the Mashriqu'l-Adhkar and adore the one God in the same spirit of truth; for the ages of darkness have passed away, and the century of light has come. Ignorant prejudices are being dispelled, and the light of unity is shining. The differences existing between nations and peoples will soon be annulled, and the fundamentals of the divine religions, which are no other than the oneness and solidarity of the human race, are being established
(Abdu'l-Baha, from a talk given at a public meeting concluding the convention of Bahá'í Temple Unity in Masonic Temple, Chicago, Illinois, 1912; The Promulgation of Universal Peace, p. 64)