Galileans - Inhabitants of Galilee. It was remarkable that they should speak in this manner, because:
(1) They were ignorant, rude, and uncivilized, John 1:46. Hence, the term Galilean was used as an expression of the deepest reproach and contempt, Mark 14:70; John 7:52.
(2) Their dialect was proverbially barbarous and corrupt, Mark 14:70; Matthew 26:73. They were regarded as an outlandish people, unacquainted with other nations and languages, and hence, the amazement that they could address them in the refined language of other people. Their native ignorance was the occasion of making the miracle more striking. The native weakness of Christian ministers makes the grace and glory of God more remarkable in the success of the gospel. "We have this treasure in earthen vessels, that the excellency of the power may be of God, and not of us," 2-Corinthians 4:7. The success which God often grants to those who are of slender endowments and of little learning, though blessed with an humble and pious heart, is often amazing to the people of the world. God has "chosen the foolish things of the world to confound the wise," 1-Corinthians 1:27. This should teach us that no talent or attainment is too humble to be employed for mighty purposes, in its proper sphere, in the kingdom of Christ; and that pious effort may accomplish much, and then burn in heaven with increasing luster for ever, while pride, and learning, and talent may blaze uselessly among people, and then be extinguished in eternal night.

Are not all these - Galileans? - Persons who know no other dialect, save that of their own country. Persons wholly uneducated, and, consequently, naturally ignorant of those languages which they now speak so fluently.

And they were all amazed, and marvelled,.... They were struck with surprise, they were as it were out of themselves, like persons in an ecstasy, not knowing what could be the cause or meaning of this:
saying one to another; the phrase "one to another", is left out in the Vulgate Latin and Ethiopic versions, and so it is in the Alexandrian copy:
behold, are not all these which speak Galilaeans? rude, unpolished, and unlearned men; who had never been brought up in any school of learning, and had never learned any language but their mother tongue; and that they pronounced with an ill grace, and in a very odd manner; and which made the thing the more astonishing to them. The apostles were inhabitants of Galilee, and so very likely were the greatest part of those that were with them: hence the Christians afterwards, by way of contempt, were called Galilaeans; as they are by Julian (x) the apostate, and others (y),
(x) Opera, par. 1. Fragment. p. 557. & par. 2. Ep. 49. p. 203, 204. (y) Arrian. Epictet. l. 4. c. 7.

Are not all these who speak Galileans? Most of the disciples to this time were. The Galileans were not generally learned men, yet now all hear, every man his own tongue.