And they were all filled with the Holy Ghost, and began to speak with other tongues, as the Spirit gave them utterance.

As the need for this revival was extremely urgent, those people filled with the Holy Ghost, started by speaking with new tongues.

Why were they all speaking?

This is to make the purpose clearer to us, that the power to witness, was a basic reason why the Holy Spirit came upon the Apostles.

What were they speaking with the new tongues?

"Acts 2:7-11 KJV

And they were all amazed and marvelled, saying one to another, Behold, are not all these which speak Galilaeans? [8] And how hear we every man in our own tongue, wherein we were born? [9] Parthians, and Medes, and Elamites, and the dwellers in Mesopotamia, and in Judaea, and Cappadocia, in Pontus, and Asia, [10] Phrygia, and Pamphylia, in Egypt, and in the parts of Libya about Cyrene, and strangers of Rome, Jews and proselytes, [11] Cretes and Arabians, we do hear them speak in our tongues the wonderful works of God."

The Spirit made them speak the gospel, "wonderful works of God"

No one taught the other the new tongues. So run from the teachers of tongues, they are fake. 

It's no longer the Holy Spirit it's human spirit, it's no longer a new tongue, it's an old tongue if someone has to teach you. Beware!

Ever since, speaking in New tongues has been the evidence of Holy Ghost baptism, maybe not always in other people's languages, because they are not around to hear us, but the Holy Spirit takes over our intercession.

One more thing from our text was that, "everyone was filled" the Holy Spirit can never be exhausted, ask for your portion.

Prayers: Oh Lord, I receive the in-filling of the Holy Spirit and audacity to speak as He gives utterance, for the mighty revival.