December 21

And, now that this all-important Work may suffer no neglect, but rather function vigorously and continuously in every part of the Bahá’í world; that the unity of the Cause of Bahá’u’lláh may remain secure and inviolate, it is of the utmost importance that in accordance with the explicit text of the Kitáb-i-Aqdas, the Most Holy Book, in every locality, be it city or hamlet, where the number of adult (21 years and above) declared believers exceeds nine, a local “Spiritual Assembly” be forthwith established. To it all local matters pertaining to the Cause must be directly and immediately referred for full consultation and decision. The importance, nay the absolute necessity of these local Assemblies is manifest when we realize that in the days to come they will evolve into the local Houses of Justice, and at present provide the firm foundation on which the structure of the Master’s Will is to be reared in future. 
(Shoghi Effendi, excerpt from a letter dated March 12, 1923, to the Baha’is throughout America, Great Britain, Germany, France, Switzerland, Italy, Japan and Australasia; ‘Baha’i Administration’)