There is little confusion about this parable. Jesus continues His condemnation of the Sanhedrin and Temple officials. He uses another parable to paint their dire situation.
Many eastern rulers used the wedding day of the heir as a day of vestment, beginning a time of co-regency. Such a ceremony demanded that the feudal servants come and swear allegiance to the heir on the same terms as their previously sworn allegiance to the ruler. This was a life and death matter for nobles; refusal to attend was tantamount to treason.
The image Jesus draws with His words is that of a potentate with a small domain. Instead of a major kingdom with nobles, this ruler deals with VIP businessmen and farmers. They are all found pretty much in the same city. Capital cities in the Ancient Near East were often separate from the ruler’s palace. Thus, the ruler would send members of his royal staff down into the town to summon these VIPs. He would have already given them some advance notice, so this was not a surprise invitation. And these VIPs would have recognized the palace officials on sight.
But the VIPs invited to the wedding acted like it was some kind of joke. It held no significance for them, as those who worked went about their daily tasks. Those who didn’t work had the leisure to torment and even kill the royal servants. Obviously word would get back to the king. He mobilized his army and had them kill the VIPs and destroy their facilities in the city. Naturally their homes would have all been sited in the VIP quarter of town with it’s own wall, so burning them all together was pretty easy.
Next, the king then told his remaining staff that the wedding must go on as planned, and the food would be consumed. They were to go out and summon all the lesser folk regardless of their social status, even beggars and stable hands, and bring them to the wedding feast. Unstated is the long tradition in the Ancient Near East of kings issuing fine wedding garments to his guests. It was part of their reward for swearing loyalty to the heir. Thus, everyone who showed up could proceed with pomp and lavish ceremony. The implication is that these random folks would have all been given fancy outfits to wear to the wedding. There would have been at least as many garments prepared as there were seats in the dining hall.
This would have been quite a party lasting several days. The doors were locked and guarded the whole time to keep out the riffraff. As the king moves through the dining hall greeting his guests, he sees one person who quite obviously rejected the king’s provision of a wedding garment. Once more, this is a grave insult. The initial start of the wedding would have been during hours of darkness, so this ungrateful wretch was bound and tossed out by the guards into the dark night. Further, it was a serious social scandal to be invited to a grand wedding and then be kicked out like that. Thus, Jesus describes it as something worthy of deep regret. This reject became a total outcast, and those who managed to stay would be obliged to ostracize him after they emerged from the celebration.
Jesus ends the story with a line that says God always makes a way for just about anyone to swear allegiance and enjoy the blessings of His favor, but it seems there will always be few who actually accept the terms of the covenant kinship He offers.