So they asked him, "Teacher, we know that you are right in what you say and teach, and you show deference to no one, but teach the way of God in accordance with truth. Is it lawful for us to pay taxes to the emperor, or not? But he perceived their craftiness and said to them, "Show me a denarius. Whose head and whose title does it bear?" They said, "The emperor's." HE said to them, "Then give to the emperor the thigns that are the emperor's, and to God the things that are God's." And they were not able in the presence of the peopel to trap him by what he said; and being amazed by his answer, they became silent. (NRSV)
This is one of a series of "entrapment" questions. The next one is by Sadducees trying to find a logical problem in the resurrection based upon levirate marriage. But this current passage on the denarius is often discussed in terms of whether Christians should pay taxes or not, and they read it as a ringing endorsement. I am not so sure. The most interesting part of this passage to me is that Jesus had to ask for a denarius. Did he not have one himself? In the progression of the story of Luke-Acts, probably not! Jesus, we have seen time and again, has insisted that to become his follower, you must sell all that you own and give the proceeds to the poor. In that instance, they have nothing to "render unto Caesar." In fact, only his opponents have the coin with the figure of the emperor on it. This, in fact, is double-trouble. 1) as noted, as a follower of Jesus, you wouldn't have any money, you cannot follow Jesus and keep your property, you cannot serve both God and Mammon, but 2) it has an IMAGE on it. Images of human (and animate) figures are prohibited in this period as an "engraved image." Jews at different times and places have interpreted this strictly and loosely. In a few hundred years from Jesus' time, synagogues would pop up with clear figural representations of biblical figures and even a Helios (sun-god) image in zodiacal mosaics! But in Jesus' time, it seems this was more strictly kept. Even Herod's palaces keep to geometric and floral designs and does not have any engraved images of animate figures. To be carrying around engraved images (on coins) may have been a problem. Even so, Jesus doesn't make a big deal over this point so much in Luke-Acts (perhaps because Luke's largely Greek audience wouldn't care), but the emphasis is placed upon not having a coin to pay to the emperor.
But this does return us to the serving God versus Mammon. This Mammon, this money, has a face, the face of an emperor. In the eastern Mediterranean, more so than the western portion, emperor worship was prevalent. It was not "enforced" as it was in later centuries, but present nonetheless. In the "emperor cult" would one offer worship, perhaps light some incense, or whatever, to an image of the emperor and a female goddess, Roma, the representation of Rome.
Jesus, however, does not have this coin. Or ANY coin for that matter. Jesus and his followers will not be paying taxes to the emperor, because they do not have anything with his image. This passage, it seems, is meant to complicate, or confuse the question posed. He shifts the grounds of debate, throws the issue right back at his questioners. The result is amazement. In short, much like Socratic method, he has reduced his interlocutor to aporia. They are without recourse. Indeed, for shame! They actually have a coin to give as taxes! Instead, Jesus has recused himself from the entire economic apparatus of the imperium. Just imagine if everyone did that? Perhaps the kingdom of God would break through.