Albert Barnes on Luke 14:17

Sent his servant. An invitation had been sent before, but this servant was sent at the time that the supper was ready. From this it would seem that it was the custom to announce to those invited just the time when the feast was prepared. The custom here referred to still prevails in Palestine. Dr. Thomson (The Land and the Book, vol. i. p. 178) says

"If a sheikh, beg, or emeer invites, he always sends a servant to call you at the proper time. This servant often repeats the very formula mentioned in Lk 14:17: Tefuddulu, el asha hader--Come, for the supper is ready. The fact that this custom is mainly confined to the wealthy and to the nobility is in strict agreement with the parable, where the certain man who made the great supper and bade many is supposed to be of this class. It is true now, as then, that to refuse is a high insult to the maker of the feast, nor would such excuses as those in the parable be more acceptable to a Druse emeer than they were to the lord of this great supper." (l) "Come, for all" Prov 9:2,5, Song 5:1, Isa 55:1,2