Matthew 22:15-22 (also in Mark 12 & Luke 20) gives us the account of Jesus answering the Herodians and disciples of the Pharisees in one of their feeble attempts to make Him look foolish. His famous answer to them was, "Render to Caesar the things that are Caesar's, and to God the things that are God's," although the second half of that statement is often left out.
Many people use the response of Jesus to try and teach unlimited submission of government. Since all our American money is owned by the Federal Reserve (a private, for-profit company by the way) we shouldn't have any qualms about paying taxes no matter what they go towards, even the tens of millions of taxpayer dollars that go towards funding abortions in foreign nations.
Through mind-boggling eisegesis, many "Christians" will use Matthew 22:21 to propose that since Caesar was owed his money, we all should owe our government anything it asks for. But as I said above, this leaves out the second part of the verse. Adam Clarke explains it very well:
"The government that charges itself with the support and defense of the whole, should have its unavoidable expenses, however great, repaid by the people, in whose behalf they are incurred; therefore we should pay tribute.
But remember, if Caesar should intrude into the things of God, coin a new creed, or broach a new Gospel, and affect to rule the conscience, while he rules the state, in these things Caesar is not to be obeyed; he is taking the things of God, and he must not get them."
We forget that there are things which we owe to God that cannot be handed over to any government.
It's also important to note that the word translated "render" (αποδιδωμι) as in "render unto Caesar" means to give back to. It means that since the coin had his image on it, and it was his to begin with, we ought to give it back to him. My freedom, my conscience, my family, are NOT things stamped with the image of the government and were not given to me by the government. Therefore they are not eligible to be rendered unto the government. My freedom, my conscience, my family, were given to me by Almighty God and He is owed all those things! Let's not forget to give back to God that which is made in His image and serve Him with our lives.
"Ye are bought with a price; be not ye the servants of men." - 1 Corinthians 7:23