A great, very funny word is used in this verse the only time by Jesus. It is translated as "murmured/grumbled" but the word reads funny in any language, goggyzon. The tense is the simple past, which is odd because this parable is mostly told in the special tense, "at that time" of Greek, with some lapses into the present tense and past perfect. This word, however, indicates an activity that started in the past but wasn't completed. So, the grumbling continues until today. Which is funny.
The "saying" here that ends the verse better belongs with the next verse. It did in the KJV version, but not in the older Greek sources.
Christ's Words in Matthew as a Guide to 40 Days of Prayer.