Lu 17:19 ..."Your faith has made you well."
It's an elliptical statement. You have to read between the lines when you read this: "Your faith in Me has made you well." If you read the context, the leper here was pleading for the Lord Jesus Christ to heal him, and the Lord granted his request.
He knew who he was. He knew that he had a disease which he can't do anything about. But he also knew Christ and what He can do. He had faith in Him and he was made well. Faith in Christ was enough for Christ is enough. It's a case of being made well by faith alone.
It's a picture of salvation. It's a portrait of what He can do for us sinners. We are incurably sick spiritually. We need healing badly. The Lord Jesus Christ comes to us through the Gospel message, and the moment we put our faith in Him and what He did on the cross for us, we will be made well...we will be saved.