USBN #178 December 1945 p1
Regarding the whole question of an international language and its relation to the Faith: We, as Bahá'ís, are very anxious to see a universal auxiliary tongue adopted as soon as possible; we are not the protagonists of any one language to fill this post. If the governments of the world agree on an existing language, or a constructed, new tongue, to be used internationally, we would heartily support it because we desire to see this step in the unification of the human race take place as soon as possible.
Esperanto has been in wide use, more so than any similar language, all over the world, and the Bahá'ís have been encouraged by both the Master and the Guardian to learn it and to translate Bahá'í literature into it. We cannot be sure it will be the chosen language of the future; but as it is the one which has spread most, both East and West, we should certainly continue to co-operate with its members, learn to speak it, and translate Bahá'í literature into it.
– to John M. Clifford October 17, 1944