The background of this sentence is that people who are dissatisfied with Jesus' teachings have raised an embarrassing question for Jesus, that is, how to deal with the relationship between religion and secular regime. "God belongs to God and Caesar belongs to Caesar" is Jesus' answer. Because at that time, the highest authority in Palestine was the Roman Empire, and Caesar was the floorboard of the Roman emperors. This sentence means that the railway police, each in charge of a section, exclude the river.