As they were gathering in Galilee, Jesus said to them, "The Son of Man is going to be betrayed into human hands, and they will kill him, and on the third day he will be raised." And they were greatly distressed. When they reached Capernaum, the collectors of the temple tax came to Peter and said, "Does your teacher not pay the temple tax?" He said, "Yes, he does." And when he came home, Jesus spoke of it first, asking, "What do you think, Simon? From whom do kings of the earth take toll or tribute? From their children or from others?" When Peter said, "From others," Jesus said to him, "Then the children are free. However, so that we do not give offense to them, go to the sea and cast a hook; take the first fish that comes up; and when you open its mouth, you will find a coin; take that and give it to them for you and me."
Since children of the kings of the earth are exempt from the taxes of the king even more so are the apostles exempt from the payment due to the temple being as they are free children of God. Even so, to avoid giving offense Jesus produces the required payment by means of a small miracle which still serves to teach in itself: money is base and earthly and not worthy to be prized. We are shown that even though something may be true it is not always worth pressing the point and giving offense. Moreover, we are taught to obey the authorities. "For the same reason you also pay taxes, for the authorities are God's servants...Pay to all what is due them - taxes to whom taxes are due..." (Romans 13.6-7) "For the Lord's sake accept the authority of every human institution." (1 Peter 2.13)
"What do you think, Simon?" Jesus sometimes teaches us by getting us to think about the issue for ourselves first. When we start to work it out in our mind he will illuminate us but he wants us to take the initial step ourselves, like a mother teaching her child to walk. This is not so we can be independent, free thinkers but so that he can lead us on to ever deeper truths.