“The more universal and informal the character of Bahá'í worship in the Temple the better. Images and pictures, with the exception of the Greatest Name, should be strictly excluded.”

First Baha'i Temple

As to the character of the meetings in the auditorium of the Temple, he feels that they should be purely devotional in character, Bahá'í addresses and lectures should be strictly excluded. For the present he feels that there would be no objection to having Bahá'í meetings, including addresses and the business sessions of the Convention, held in the Foundation Hall. Shoghi Effendi would urge that 'choir' singing by men, women and children be encouraged in the auditorium and that rigidity in the Bahá'í service be scrupulously avoided. The more universal and informal the character of Bahá'í worship in the Temple the better. Images and pictures, with the exception of the Greatest Name, should be strictly excluded. Prayers revealed by Bahá'u'lláh and the Master, as well as the sacred writings of the Prophets, should be read or chanted, as well as hymns based upon Bahá'í or non-Bahá'í sacred writings. 

- Shoghi Effendi  (From a letter dated 11 April 1931 written on behalf of Shoghi Effendi to the National Spiritual Assembly of the United States and Canada; The Compilation of Compilations, Vol. III, Service in Baha’i Temples)