When God calls, we should listen. When God gives us a calling, we should embrace it. Isaiah was one of the Old Testament prophets that was not very hesitant with his calling. Isaiah heard God speak, and embraced the calling.
Note that, when Isaiah heard the voice of the Lord, he did not hear it by accident. God knew that Isaiah heard Him. This was part of God's plan the entire time. God allowed the specific person that He intended to accept this calling to hear His words. In other words, God allowed Isaiah to hear Him because He intended the message for Isaiah.
Also note that God did not ask whether or not He would send anyone. Rather, God asked WHO He should send. This question was asked rhetorically. God already knew the answer. God had a calling for Isaiah, and intended to send him to fulfill that calling. Isaiah was to go for God.
Notice also that Isaiah responded immediately and voluntarily. Isaiah could have responded in a different way. Isaiah could also have decided not to go. However, Isaiah did not hesitate in accepting the call that God had for his life.
How do we respond? How many of us have heard God ask this same question, yet have refused to respond like Isaiah? Why don't we choose today to respond like Isaiah did? God already knows the answer to the questions He asks. We do not hear Him speak by accident. What is stopping us from responding like Isaiah did?