The Kitáb-i-Aqdas
193.Select ye a single language … adopt ye … a common script.   ¶189
Bahá’u’lláh enjoins the adoption of a universal language and script. His Writings envisage two stages in this process. The first stage is to consist of the selection of an existing language or an invented one which would then be taught in all the schools of the world as an auxiliary to the mother tongues. The governments of the world through their parliaments are called upon to effect this momentous enactment. The second stage, in the distant future, would be the eventual adoption of one single language and common script for all on earth.
Other Related References
Divine Philosphy,   pp. 141-146
Paris Talks,   pp. 155-158
Bahá’í International Community
October 1995, Turning Point for All Nations,   item A4
Tablets of Bahá’u’lláh
Kalimát-i-Firdawsíyyih,   p. 68
Lawḥ-i-Maqṣúd,   pp. 165-166
Gleanings from the Writings of Bahá’u’lláh,   CXVII, pp. 253-254
Lights of Guidance
Languages,   pp. 340-341 (1137-1143)
Principles of Bahá’í Administration,   27
The Compilation of Compilations,   pp. 151-152, no. 1566
Dr J.E. Esslemont
Bahá’u’lláh and the New Era,   pp. 163-165