Adam Clarke on Acts 2:4

To speak with other tongues - At the building of Babel the language of the people was confounded; and, in consequence of this, they became scattered over the face of the earth: at this foundation of the Christian Church, the gift of various languages was given to the apostles, that the scattered nations might be gathered; and united under one shepherd and superintendent (επισκοπος) of all souls.

As the Spirit gave them utterance - The word αποφθεγγεσθαι seems to imply such utterance as proceeded from immediate inspiration, and included oracular communications.