On 28 November 1921, `Abdu'l-Bahá passed away peacefully in His sleep. Like His father, `Abdu'l-Bahá was concerned with the potential for religious schism after His passing. So He, too, left a clear and explicit will and testament--an extension of the Covenant established by Bahá'u'lláh. 

In that document, `Abdu'l-Bahá appointed His oldest grandson, Shoghi Effendi Rabbani, to succeed Him as Guardian of the Bahá'í Faith. The Guardianship was an institution anticipated by Bahá'u'lláh. 

In this office, Shoghi Effendi was the authoritative interpreter of the Bahá'í teachings.
  

The letters of Shoghi Effendi also developed guidelines for the system of elections and group decision-making that has become one of the Bahá'í Faith's distinguishing features. He wrote letters to fledgling Bahá'í institutions that explained the implications of Bahá'u'lláh's teachings on issues ranging from family life to world government. He elaborated on the relationship of the Bahá'í Faith to other religions and doctrines. His lucid and incisive writings further helped to clarify the distinctive Bahá'í views on matters of ethics, theology and history. 

Perhaps most important, insofar as the growth of the Bahá'í Faith is concerned, Shoghi Effendi's letters to the Bahá'í world provided a continuing source of encouragement and support. Although the Bahá'í Faith today enjoys wide respect, to become a Bahá'í in the 1930s, 1940s, or 1950s was to expose oneself to suspicion and ridicule. 

Shoghi Effendi's clear vision of the Bahá'í Faith as God's revelation to our age, and his certainty of its ultimate triumph, helped to invigorate a generation of believers who, though few in number, were responsible for having spread Bahá'u'lláh's message to every corner of the globe.