There is a sharp contrast between the rule of Cyrus the Great, in the reading from Isaiah, and that of the Imperial government of Rome, referred to in the gospel. Cyrus had the reputation of being a just ruler, who respected the customs of his conquered subjects and even learnt from them. Though he did not share Jewish beliefs, he allowed their exiles to return home from Babylon and even helped them rebuild their temple. The Romans, on the other hand, exacted heavy taxes from the Jewish people and imposed harsh punishments on those who defied them.
The Herodians were supporters of the family of Herod, who collaborated with the Romans in order to maintain his position. The Pharisees, who were very devout and strict observers of the Law, were hostile to their alien rulers with their pagan culture. They especially resented the poll tax, which was paid to an earthly sovereign, when God was regarded as ruler of Israel. Additionally, the denarius was stamped with the image of the Emperor, violating the Second Commandment, which forbade the use of graven images. Thus the Herodians and Pharisees were normally at odds with each other. On this occasion, however, it suited the two parties to come together to trap Jesus. It was a dangerous situation for him. If he said it was lawful to pay the tax the Pharisees would be offended; if he said it was not lawful, then Herodians would be fearful of Roman retaliation.
His reply was astute, as it did not specifiy exactly what was Caesar’s but indicated that whatever was rightfully the Emperor’s should be given to him. Jesus was approaching the end of his life, and Matthew probably wanted to make it clear that Jesus was not a rebel. He told Pilate: “My Kingdom is not of this world” (John 18:36).