A friend enquired concerning Bahá’u’lláh's prophecy in the Words of Paradise, that a universal language would be formed, and desired to know if Esperanto would be the language chosen. "The love and effort put into Esperanto will not be lost," he answered, "but no one person can construct a Universal Language. It must be made by a Council representing all countries, and must contain words from different languages. It will be governed by the simplest rules, and there will be no exceptions; neither will there be gender, nor extra and silent letters. Everything indicated will have but one name. In Arabic there are hundreds of names for the camel! In the schools of each nation the mother tongue will be taught, as well as the revised Universal Language."

‘Abdu’l-Bahá, ‘Abdu’l-Bahá in London, p. 93

Esperanto has been drawn up with this end in view: it is a fine invention and a splendid piece of work, but it needs perfecting. Esperanto as it stands is very difficult for some people.

‘Abdu’l-Bahá, Paris Talks, p. 156

His Holiness Bahá’u’lláh, many years ago, wrote a book called The Most Holy Book, one of the fundamental principles of which is the necessity of creating an auxiliary language, and he makes clear the good and profit which will come because of its use. Now let us thank the Lord because this language, Esperanto, has been created. We, therefore, have commanded all Bahá’ís in the East to study this language very carefully, and ere long it will be spread through the entire East. I also beg of you all, Esperantists and non-Esperantists, to work energetically for the spread of this language, for it will hasten the coming of that day, that millennial day, foretold by prophets and seers, in which it is said that the wolf and the lamb shall drink from the same fountain, the lion and the deer shall feed in the same pasture. The meaning of this holy writing is that hostile races, warring nations and differing religions shall become united in the spirit of love, and will become bound together, one with the other.

‘Abdu’l-Bahá, Star of the West, v6, p. 287

His Honor, Dr. Fareed – Upon him be Bahá-el-Abhá! O servant of the Holy Threshold! You have written in regard to Esperanto and your speech before the Congress. It was appropriate and acceptable. If possible meet with Dr. Zamenhof and show him the Kitab-el-Aqdas (Book of Laws) and translate the verse which concerns the Universal Language and tell him: This clear verse, which was revealed forty-five years ago, will prove the cause of spreading your Universal Language in all the East. The Bahá’ís shall consider the study of this language as an incumbent duty upon them, and it will be to them a religious duty. Therefore, men, women, and children, all will acquire it.

‘Abdu’l-Bahá’s letter to Dr. Ameen Fareed based on the original as published in The British Esperantist, Dec. 1911

It is our hope then, that the language Esperanto will soon spread throughout the whole world, in order that all people may be able to live together in the spirit of friendship and love.

‘Abdu’l-Bahá, Bahá’í Scriptures, p. 339

May it be promulgated rapidly; then the world of humanity will find eternal peace; all the nations will associate with one another like mothers and sisters, fathers and brothers, and each individual member of the community will be fully informed of the thoughts of all.

‘Abdu’l-Bahá, Divine Philosophy, p. 146