In the beginning, God created the heavens and the earth. There was darkness, and He said let there be light. Whatever God wants to do, He does by His word, by speaking.  And the same God who created everything by His voice decided to come to this earth in the person of Jesus. 

Jesus also spoke, and the earth responded. He cursed the fig tree, and it withered.

If our God is a speaking God, and we are offspring of Him, then we must be a people who speak.

One of the most important characteristics of God that must be evident in us is prophecy. Everything God did, He said it first. And so God can give utterance for prophecy just as He gives for tongues, that there will be no guesswork, that precision can be given.