Jesus" questions highlighted the ingratitude of the nine other lepers who were Jews ( Luke 17:18). They also made the point that Luke wanted to stress by recording this incident. The Jews had more knowledge about Messiah and His coming than foreigners. They should have recognized who Jesus was and expressed their gratitude as well. Their lack of responsiveness was typical of the Jews in Jesus" day (cf. Luke 15:3-10). In closing, Jesus clarified that it was the man"s faith in Him that led to his obedience and was responsible for his restoration, not just his obedience. Jesus was not implying that the other nine lepers lacked faith. They also believed in Him ( Luke 17:13). [source][source][source]
The incident teaches that people whom Jesus delivers and who believe on Him have a moral obligation to express their gratitude to Him for what He has done for them. It also illustrates the fact that the Jews were happy to receive the benefits of Jesus" ministry without thanking Him or connecting His goodness with God. The chiastic structure of Jesus" three questions ( Luke 17:17-18) is another indication that the focus of attention is on the ingratitude of the nine healed lepers. [source][source][source]