John the Baptist calls people to repent and be immersed (baptised). Some in the crowd ask ‘What must we do’. After John answers them, a Roman soldier asks John ‘What should we do?’
You can almost sense the tension in the air. The Jews would almost certainly have been on edge. Why is this soldier asking this question? Has this pagan suddenly had a conversion experience? Is this just a naked act of provocation?
Since Rome did not interfere in local religious matters, the only reason the soldier is there is to make sure no-one is plotting the overthrow of the Roman occupiers. In other words, he is baiting John to see whether he is a trouble maker. And the answer John gave could well have cost him his life! Not sure what the answer was? Read the story in Luke 3.