Acts 2:36

Let all the house of Israel therefore know assuredly, that God hath made him both Lord and Christ, this Jesus whom ye crucified.

All the house of Israel ... There seems to be good reason to understand these words as being addressed not to the dwellers in all those countries mentioned by Luke (Acts 2:8-12), but to the Jews of the Holy City itself, there being no evidence that the Diaspora had taken any hand in the rejection of Christ. This justifies the conclusion that the "speaking" of all the Twelve in languages they had never learned, earlier that morning, was not in any sense a preview of this sermon. This sermon was the first of the gospel age, quite properly delivered "to the Jew first" as God had ordained; and, therefore, it may be concluded, that those earlier "speakings" were concerned with gathering an audience for Peter's message, the same purpose being evident in the rushing sound and other divine manifestations of that hour.