A.T. Robertson Commentary Luke 17:16

"and he fell upon his face at his feet, giving him thanks: and he was a Samaritan." — Luke 17:16 (ASV)

And he was a Samaritan (κα αυτος ην Σαμαρειτης). This touch colours the whole incident. The one man who felt grateful enough to come back and thank Jesus for the blessing was a despised Samaritan. The αυτος has point here.