“Then he said to them, ‘So give back to Caesar what is Caesar’s, and to God what is God’s.’” (Matthew 22:21b, NIV)
We know what belongs to Caesar. Caesar’s name is on his money. Caesar collects his tax from wages, even before it is deposited in our personal accounts. Caesar has laws for conduct that must be obeyed under penalty of fine or imprisonment. We get it, and we render to Caesar what belongs to Caesar because it is right to do so.
On the other hand, what belongs to God?
For an answer, we need look no further than the first book of the Bible (Genesis), where we see that we each were created in the image and likeness of God. As coin and currency bears the image and likeness of Caesar (a.k.a civil government), it is God’s image only that is borne by you and me.
While Caesar is about possessions and property, God is always about persons. We belong to God, and God desires our fellowship. He desires nothing more; and we should offer Him nothing less. – Luther
Daily Encouragement 
Luther, Does this mean that I’m not expected to Tithe? or give to the Church? PAX, Dick+ < 🙂
Dick, a good question; but knowing you as I do, I suspect that you already know the answer.
For the benefit of readers who might not be in on our private “give and take,” I think the answer is found in the original question: What belongs to God? The tithe (literally, “tenth”) that we may give to the church is, in its purest form, a joyful acknowledgement of the universal lordship of God rather than a grudging rendering of a tax come due. If we are not inclined to return a portion of God’s blessings to His work on this earth, perhaps it is because we are not truly convinced of His universal lordship. If we were, our joy in the relationship we are privileged to have with Him would manifest itself in how we chose to spend our time, talent and — yes — our treasure. Thanks for the opportunity to give a fuller explanation, Dick!