16 And they began to speak with other tongues as the Spirit gave them utterance. The Galilean Peter or Andrew spoke Persian or Median. John and the rest of the Apostles spoke every tongue to those of Gentile extraction; for not in our time have multitudes of strangers first begun to assemble here from all quarters, but they have done so since that time. What teacher can be found so great as to teach men all at once things which they have not learned? So many years are they in learning by grammar and other arts to speak only Greek well; nor yet do all speak this equally well; the Rhetorician perhaps succeeds in speaking well, and the Grammarian sometimes not well, and the skilful Grammarian is ignorant of the subjects of philosophy. But the Holy Spirit taught them many languages at once, languages which in all their life they never knew. This is in truth vast wisdom, this is power divine. What a contrast of their long ignorance in time past to their sudden, complete and varied and unaccustomed exercise of these languages!
Source: Catechetical Lectures (New Advent)