The Kitáb-i-Aqdas - The Most Holy Book
Index term: Administrative Order, Bahá'í
n82.
Verily, it is enjoined upon you to offer a feast, once in every month
This injunction has become the basis for the holding of monthly Bahá'í festivities and as such constitutes the ordination of the Nineteen Day Feast. In the Arabic Bayán the Báb called upon His followers to gather together once every nineteen days to show hospitality and fellowship. Bahá'u'lláh here confirms this and notes the unifying role of such occasions.
'Abdu'l-Bahá and Shoghi Effendi after Him have gradually unfolded the institutional significance of this injunction. 'Abdu'l-Bahá emphasized the importance of the spiritual and devotional character of these gatherings. Shoghi Effendi, besides further elaborating the devotional and social aspects of the Feast, has developed the administrative element of such gatherings and, in systematically instituting the Feast, has provided for a period of consultation on the affairs of the Bahá'í community, including the sharing of news and messages.
In answer to a question as to whether this injunction is obligatory, Bahá'u'lláh stated it was not (Q&A 48). Shoghi Effendi in a letter written on his behalf further comments:

Attendance at Nineteen Day Feasts is not obligatory but very important, and every believer should consider it a duty and privilege to be present on such occasions.
n114.
Carmel . . . Zion
Carmel, the "Vineyard of God", is the mountain in the Holy Land where the Shrine of the Báb and the seat of the world administrative centre of the Faith are situated.
Zion is a hill in Jerusalem, the traditional site of the tomb of King David, and is symbolic of Jerusalem as a Holy City.
n189.
this new World Order
In the Persian Bayán, the Báb stated: "Well is it with him who fixeth his gaze upon the Order of Bahá'u'lláh, and rendereth thanks unto his Lord. For He will assuredly be made manifest. God hath indeed irrevocably ordained it in the Bayán." Shoghi Effendi identifies this "Order" with the System Bahá'u'lláh envisages in the Aqdas, in which He testifies to its revolutionizing effect on the life of humanity and reveals the laws and principles which govern its operation.
The features of the "new World Order" are delineated in the Writings of Bahá'u'lláh and 'Abdu'l-Bahá and in the letters of Shoghi Effendi and the Universal House of Justice. The institutions of the present-day Bahá'í <span class="highlight">Administrative Order, which constitute the "structural basis" of Bahá'u'lláh's World Order, will mature and evolve into the Bahá'í World Commonwealth. In this regard, Shoghi Effendi affirms that the Administrative Order "will, as its component parts, its organic institutions, begin to function with efficiency and vigour, assert its claim and demonstrate its capacity to be regarded not only as the nucleus but the very pattern of the New World Order destined to embrace in the fullness of time the whole of mankind".
For additional information on the evolution of this new World Order, see, for example, the letters of Shoghi Effendi published in The World Order of Bahá'u'lláh.