Mat 22:11 And when the king came in to see the guests, he saw there a man which had not on a wedding garment:
Mat 22:12 And he said to him, Friend, how did you come in here not having a wedding garment? And he was speechless.

Just when we thought the story was over, it has a very important postscrip. The kingdom of heaven isn't only about accepting the invitation to the feast, it is about something more.

Christ uses clothing as a sign of wealth. All matters of wealth are part of the mental realm, which focuses on thoughts and words. This parable is largely about communication, that is, the message of the king about the wedding.

While Christ doesn't want people to get trapped by worrying about wealth and, therefore, there clothing ("the lilies of the field"), his teaching is that the physical-mental-emotional must be connected. Without thought and words, we cannot have relationships. This parable is about the need for us to be aware of the messages otehrs are sending us and we are sending them. Specifically in these verses, this wedding guest's clothing is saying something about his feelings about his relationship with the king.

Christ used the term "wedding garment" in much the same way as we would describe someone wearing their "Sunday best." From my research, the minimum requirement at the time seems to be simply to have clean clothing. Again, like wearing your Sunday best, the idea is to show respect to the host and the other guests.

Notice how kindly the king at first addresses the offending guest. Rather than getting angry, he addresses the man in a friendly way and asks for an explanation. It wasn't until the offending guest offers no explanation that the king becomes insulted, not only because the guest had no good answer but because he didn't giv the king the courtesy of an explanation or asking for forgiveness.

"Garment" is from enduma, which means "garment" or "covering."

"Friend" is from hetairos, which means "comrade," "companion," and "partner." It is a friendly form of address (through it doesn't really mean "friend"), and specifically used to describe a companion at a feast.

"Speechless" is from phimoô, which means "to muzzle," "to be silent," and "to be put to silence."