September 14

Question: What is meant by the Apostles’ speaking in tongues?

Answer: The meaning is that the Apostles taught in a spiritual tongue, a tongue that embraces all tongues. For the Word of the Kingdom comprises spiritual meanings and divine mysteries, and whoso attains to this Word will find the realities and mysteries of creation to be clear and evident. The divine inner meanings are the all-encompassing reality of all tongues.

Therefore, the Holy Spirit endowed the Apostles with the tongue of the Kingdom, and they spoke with all peoples as if in their own tongue; that is, whenever they conversed with a person of any faith or nation, it was as though they were speaking his own tongue. Were it otherwise, there are at present more than a thousand known languages and it would be fair to expect that the Apostles would have written at least one Gospel in the language of one of the other nations. It is, however, well established that the Gospel was written only in Hebrew and in Greek. No Gospel was even written in Latin, though that was at the time the official language of the land. Yet, as the Apostles were not proficient in Latin, no Gospel was written in that language. 
- ‘Abdu’l-Baha  (Table Talks at Akka; Online Baha’i Reference Library of the Baha’i World center)