'Abdu'l-Baha (1844-1921), meaning in Arabic "Servant of the Glory," was the title assumed by Abbas Effendi, the eldest son and appointed successor of Baha'u'llah. He dedicated His life to service to those in need and sharing the Baha'i teachings with people around the world. Shoghi Effendi Rabbani (1897- 1957) was appointed the Guardian of the Baha'i Faith after the passing of Abdu'l-Baha in 1921. He was the head of the worldwide Baha'i community from 1921 until his passing in 1957. He was the authorized interpreter of the Baha'i writings. Baha'u'llah (1817- 1892), meaning in Arabic " the Glory of God," is the Prophet and Founder of the Baha'i Faith. The main theme of Baha'u'llah's message is unity. He taught that there is only one God, that all the world's religions represent one changeless and eternal Faith of God, and that all humanity is one race destined to live in peace and harmony.