Luke 20:22

“Is it lawful for us to give tribute to Caesar, or not?”

Their question was as to whether it was ‘lawful' or not to give tribute to Caesar. That is whether it was in line with the teaching of Moses. Now strictly speaking the Law does not deal with that question. But the Law does make it clear that the people of Israel were God's people, God's holy nation, and thus that for them to be ruled over by anyone else was contrary to God's intention. It was something that would only happen to them as a result of disobedience. So to every Jew the answer as to whether tribute should be paid to Caesar would have been a resounding ‘No!' For while they reluctantly did on the whole give such tribute, they certainly did not see it as ‘lawful'. In their view the Law required rather that they directed their gifts towards God, His Sanctuary and His people, and the Roman poll tax was highly and deeply resented as an imposition, and as an evidence of their submission to Rome.

Thus if Jesus answered the question by declaring that it was lawful He would instantly have been denounced by the whole nation as a false prophet. On the other hand if He said that it was not lawful, (and that was the answer towards which they were working), then they could immediately denounce him to the Roman governor for stirring up the people to avoid paying their taxes, a crime subject to the most serious punishment.