Oneness of the world of humanity

A fundamental teaching of Bahá’u’lláh is the oneness of the world of humanity. Addressing mankind, He says, “Ye are all leaves of one tree and the fruits of one branch.” By this it is meant that the world of humanity is like a tree, the nations or peoples are the different limbs or branches of that tree, and the individual human creatures are as the fruits and blossoms thereof. In this way Bahá’u’lláh expressed the oneness of humankind, whereas in all religious teachings of the past the human world has been represented as divided into two parts: one known as the people of the Book of God, or the pure tree, and the other the people of infidelity and error, or the evil tree.
The former were considered as belonging to the faithful, and the others to the hosts of the irreligious and infidel—one part of humanity the recipients of divine mercy, and the other the object of the wrath of their Creator. Bahá’u’lláh removed this by proclaiming the oneness of the world of humanity, and this principle is specialized in His teachings, for He has submerged all mankind in the sea of divine generosity.

`Abdu'l-BaháThe: Promulgation of Universal Peace