Matthew 22:5

‘But they made light of it, and went their ways, one to his own farm, another to his merchandise, and the remainder laid hold on his servants, and treated them shamefully, and killed them.'

Some of his messengers who made their way back reported that on receiving the invitation, instead of preparing to set off for the wedding, some of the invitees ostentatiously went off to see to their farms and others to their businesses. It was a clear further refusal and intended to be a deliberate and open affront to the king in each case. Others sent the slaves back shamefully treated, indicating to the king what he could do with his son. Compare for this 2 Samuel 10:4, and see Jeremiah 20:2; Jeremiah 37:15. The ill-treatment and humiliation of messengers was a regular way of rejecting an overlord's invitation. It indicated what they thought of him and his messengers, and that they no longer accepted his authority over them. Others killed the messengers, possibly sending back a body part in order to indicate what they had done. Josephus tells of how when Hezekiah issued invitations to the Israelites to come to the feast of the Passover, many of those who received them killed his messengers. So these have been common ways throughout history whereby men have indicated disdainfully that they were no longer prepared to accept an overlord. (It was always dangerous to be a messenger to such people). The varying responses also indicate the varying way that people reject God's invitation to come to Him, some more violently than others. Again the prophets are in mind in the servants, including especially John the Baptist, the latest prophet to be martyred. And they were already planning to do the same thing to Jesus.