Well, what I see in Luke 17:14 is the healing power of God in operation, which is available to everyone of us if we believe and obey just as the Lepers. You remember 1 Peter 2:24, by his (Jesus) stripes we are healed. The same God"s healing power in operation.' applies to me ' , could you elaborate what you mean by that ? For example how would this verse ' apply' to you?
Luke 17 .
14¶And when he saw them, he said unto them, Go shew yourselves unto the priests. And it came to pass, that, as they went, they were cleansed.
And this one by Jesus also:
Matthew 10:5
“These twelve Jesus sent forth, and commanded them, saying, Go not into the way of the Gentiles, and into any city of the Samaritans enter ye not:”
When we come across the scripture on the great Commission and realise that the spreading of the good news of the gospel is no longer restricted to the Apostles or to the Jews, our understanding of the scripture you quoted in Matthew 10: 5 widens. Even at that, we may want to know, why they were restricted in that manner, What spiritual lessons are there for us if any? The Holy Spirit is there to guide us.