It seems like the Pharisees are constantly trying to trick Jesus into saying something that would get Himself into trouble, and today's Gospel is no exception. It seems an innocuous question regarding taxes, but is a cleverly devised trap that they think will cause Him to either go against the Jewish faith or the Roman authorities. Instead of falling into their trap, Our Lord once again shows us how far God is above anything we can comprehend.
At the time of Jesus, the Jewish people were under the control of the Roman Empire. The Roman coins had the image of Caesar stamped on them, and were forbidden to Jews by the strictures in the Mosaic Law against graven images. The Roman money wasn't even allowed into the temple, thus the moneychangers within the temple precinct. If Jesus would have outright allowed the tax, the Pharisees would have claimed that He was acting against this command, discrediting Him with the people.
Likewise, the Roman authorities were not popular within Palestine, as they were viewed as conquerors and occupiers. Many movements had come and gone trying to roust out the Roman military and government officials from their land, and was still a popular sentiment. If Our Lord had outright encouraged the Roman tax, the Pharisees would probably have denounced Him as a Roman sympathizer, causing those around Him to turn on Him.
The Pharisees also knew how to play both sides of the fence. If Our Lord would have spoken against the Roman tax, the Pharisees would have immediately reported Him to the Romans calling him a revolutionary who wanted to overthrow the Roman governance, starting with the Roman taxes. Rome was not known for being well-disposed to revolutionaries within their realms, so their response would have been very swift and brutal against Our Lord.
Jesus refuses to fall into their trap, and uses this as a teaching opportunity to make the distinction between the things of the world and that which is dedicated to God. By “[giving] to Caesar what is Caesar's”, Our Lord is talking about the things of the world, our possessions, our money, even the essentials that we need for basic survival. He's not saying that these things are bad, or wrong to have and keep, but that they are the things of the world and could be taken away by the worldly authorities at any time. Even our very lives on earth could be taken away by civil authorities or military force.
While our life on earth is subject to the authority and power of the Caesars of the world, everything we have and are is God's. The earthly governments could take away everything we own, even our lives, but they cannot destroy our essence, who we are. God has promised us that we will have eternal life with Him, if we choose to join Him at the end of our earthly lives. The governments and powers of the world cannot take that away from us unless we allow it. Our very existence is a gift from God, and no earthly power can do more than end our life on earth.
Because our lives and even our very existence are gifts from God, we are called by Our Lord to dedicate ourselves serving God. We serve him by living out our vocations to the fullest, while also spreading the Gospel message that Jesus died for our sins and wants us in relationship with the Father. This doesn't mean that we have to stand on the street corner preaching, but that we have to live the Christian virtues in our daily lives, treating all those we meet on a daily basis with true charity and respect.
Sometimes living out the Christian life means a willingness to give up our lives in service of the Gospel. We are very fortunate in this country that we are not called to martyrdom for merely being Christians. In other countries, however, being a Christian is at best a jailable offense, and could even lead to death. These martyrs show us the example of how to truly dedicate oneself to God, even being willing to give up one's life for Christ.
Through the example of a simple coin, Our Lord shows us that all that we are is God's, and that we must be willing to serve Him. May we have the strength to dedicate ourselves to Him.