The Necessity of Increased Faith
It is a matter of dispute as to the occasion when these words were uttered. Some think that we must look at the connection of the chapter for the explanation. Jesus Christ had been teaching his disciples that if their brother should trespass against them seven times a day, and seven times a day turned again to them, saying, I repent, they were to forgive him, and that constrained the apostle to say "increase our faith." They conceived it to be so hard a duty incessantly to pardon and constantly to …
Charles Haddon Spurgeon—Spurgeon's Sermons Volume 1: 1855

Li. Gratitude.
14th Sunday after Trinity. S. Luke xvii. 18. "There are not found that returned to give glory to God, save this stranger." INTRODUCTION,--There is nothing that the merciful God desires more from man than thanks, and there is nothing of which He receives less. In the Gospel for to-day we have an example. Christ performs a notable miracle. He heals ten lepers, and only one returns to thank Him. The disease from which He delivered them was disgusting, and it was one which cut the sufferers off …
S. Baring-Gould—The Village Pulpit, Volume II. Trinity to Advent

The Ten Lepers
(Fourteenth Sunday after Trinity.) Luke xvii. 17, 18. Were there not ten cleansed, but where are the nine? There are not found that returned to give glory to God, save this stranger. No men, one would have thought, had more reason to thank God than those nine lepers. Afflicted with a filthy and tormenting disease, hopelessly incurable, at least in those days, they were cut off from family and friends, cut off from all mankind; forced to leave their homes, and wander away; forbidden to enter the …
Charles Kingsley—Town and Country Sermons