After the Holy Spirit fell down upon the Apostles and all those within the house where they were gathered for prayer, the Apostles began to speak in tongues. Many Jews scattered across the Roman and Parthian Empires were attending the Feast of Pentecost and wondered what was taking place. All seemed to be hearing the Apostles in their native tongues. That is, the tongues of their homeland, not the universally understood commercial language of Greek in the West or Aramaic in the East. At this point Luke enumerates twelve different countries to which the Jews had been scattered (Acts 2:9-10). The point of the miracle was to emphasize that this was the time for the regathering of God’s people out of those places where they were scattered. The time of restoring all things to their original God-intended beauty and meaning had begun (cp. Acts 3:21).
A problem developed, because some began to mock. Why were they mocking? It is because the twelve Apostles were praising God freely in a spiritual tongue understood by all in his own native language. In Zechariah 9:9-17 we find a passage that points to these times. Jesus had come to the Jews humbly and riding upon a donkey, offering salvation (v.9; cp. Matthew 21:5). The passage directs our attention to the daughter of Zion which is the Church of God—the remnant that believes. He takes away the implements of warfare from his people and preaches peace to the heathen, and victory is implied in that his dominion is from sea to sea even to the ends of the earth (Zechariah 9:10). These are the prisoners set free by the blood of Christ (v.11). God uses them in his spiritual warfare against the nations (v.13), as though they were his battle bow and sword. All that is required is that they turn to their Stronghold (Christ) and he will give them a double portion (v.12). These have become the mighty army of God (v.14), but their implements of warfare are not conventional, but spiritual; they preach peace (v.10). The Lord is their defense as they devour and subdue, making a noise “as through wine” (v.15), and they are filled like the bowls of the altar (i.e. with the blood of the covenant), rejoicing in his goodness and great beauty (Zechariah 9:17).
This is what was occurring in Jerusalem on the day when the men from twelve countries heard the twelve Apostles praising God in their own native tongue. It was as though they were filled with wine (Zechariah 9:15, 17; cp. Zechariah 10:7). The mockers (Acts 2:13), apparently, were from Judea and Jerusalem, because Peter doesn’t address the crowd generally as he does later in v.22, but only that portion native to Judea and Jerusalem (v.14). He defends his brethren, showing it is only the third hour (i.e. 9 AM). Peter’s explanation was that the phenomena pointed to the prophecy of Joel (v.16). God was pouring out his Spirit upon those who have turned to him (Acts 2:17-18; Joel 2:28-29; cp. Zechariah 9:12), and they all shall prophecy and see visions from heaven. There will be heavenly signs (Acts 2:19-20; Joel 2:30-31; cp. Matthew 27:45 and 24:29), but those who call upon the name of the Lord (Jesus) will be saved (Acts 2:21; Joel 2:32).
Peter told the mockers that they were wrong, showing that what they witnessed was from God. It was a warning, just as the prophecy of Joel was a warning to the priests and the elders to mourn and consider what was happening in the Land (Joel 1:9-12). They are told to repent in sackcloth (Joel 1:13) and turn to the Lord (Joel 1:14) before judgment comes and it is too late (Joel 1:15). It is difficult to say how many were in the crowd who listened to Peter, but 3000 pilgrims received the message into their hearts, repenting and turning to Jesus.
 The mention of Cretans and Arabians in Acts 2:11 is meant to encapsulate the twelve mentioned in vv. 9 & 10. The universal language, Aramaic, would be understood and spoken by the “Parthians, and Medes, and Elamites, and the dwellers in Mesopotamia” (4), and they would come under the heading of Arabians or the east. Conversely, the west: Cappadocia, in Pontus, and Asia, Phrygia, and Pamphylia, in Egypt, and in the parts of Libya about Cyrene, and strangers of Rome (8) would come under the heading of Cretans.