Then Jesus asked, “Were not ten made clean? But the other nine, where are they? Was none of them found to return and give praise to God except this foreigner?” Then he said to him, “Get up and go on your way; your faith has made you well.”
The gospel writers wanted to make plain that to acknowledge Jesus as Lord was at the centre of a faithful response to God. Only one of the the ten lepers who were made clean, the despised Samaritan, returns to give thanks to Jesus and lays at his feet. All the lepers were healed. They were all made clean. But only this one is pronounced to be well. All benefitted. But this one was grateful and as a consequence of that gratefulness showed faith. Luke uses this story, like much of his gospel, to show the difference between those who become faithful followers of Jesus and those who only benefit from his work. Being healed is completed with gratitude and faith.