Some of Oswald J. Smith's favorite missionary quotes:

You must go or send a substitute.

If God wills the evangelization of the world, and you refuse to support missions, then you are opposed to the will of God.    

Attempt great things for God, expect great things from God.        

Why should anyone hear the Gospel twice before everyone has heard it once?        

Give according to your income lest God make your income according to your giving.  

Now let me burn out for Christ.