Luke 17:14

‘And when he saw them, he said to them, “Go and show yourselves to the priests.” And thus it happened that, as they went, they were cleansed.'

When Jesus became aware of them (an eyewitness touch) He commanded them to go to the priests to be examined, as though they were those who had been cured of their skin disease. We are reminded here of how Elisha commanded Naaman to go away and do something, rather than healing him on the spot. That too indicated a cleansing to come. It was calling on them for an act of faith. They still had their skin disease. But such was their faith that they went. And as they went they were healed. They were ‘made clean'. They thus no doubt then proceeded to go to the priests to obtain their certificate of cleansing, as Jesus had told them to do.