35 What could show greater obedience than that we should follow Christ's example, “Who, being found in fashion as a man, humbled Himself and became obedient even unto death?” Accordingly He has freed all through His obedience. “For as by one man's disobedience many were made sinners, so by the obedience of One shall many be made righteous.” If, then, He was obedient, let them receive the rule of obedience: to which we cling, saying to those who stir up ill-will against us on the Emperor's side: We pay to Cæsar what is Cæsar's, and to God what is God's. Tribute is due to Cæsar, we do not deny it. The Church belongs to God, therefore it ought not to be assigned to Cæsar. For the temple of God cannot be Cæsar's by right.
Source: Sermon against Auxentius (New Advent)