Jesus' Mandate: You will be my witnesses in Jerusalem, all of Judea and Samaria, and to the ends of the earth.
The harvest is great but the workers are few. There are many people that needed to hear about Jesus but few that are willing to spread the good news.
What is speaking in toungues? In verse 5, it says that when the disciples spoke, people from all nations were instantly able to understand them. They were telling all of the mighty works of God.
Sometimes God brings the mission field directly to us, rather than have us go out to the mission field. We must always be ready to be a blessing and reflect Christ when that happens.