What does Matthew 12:44 mean?

Jesus is using the analogy of a demon leaving behind a human "occupant" only to eventually return. The analogy shows what will happen to Israel if this generation does not repent of its unbelief that He is the Messiah.

The unclean spirit in Jesus' story is either cast out of a person or leaves for another reason. It passes through dry places—perhaps implying a desert (Psalm 63:1) looking for a new person to oppress. In this case, it doesn't find anyone. Now Jesus pictures the demon returning to the original person it possessed. When it comes back, the former "house" is all cleaned up. It is empty, swept, and put in order. In other words, the person had been restored to his or her right mind and is now thinking clearly and behaving normally.

Jesus is not making light of demon possession. Possession—or "oppression," as some commentators prefer—is shown throughout the gospels and Acts to be a terrible experience. Those occupied by demons lose control of their minds and bodies. They are often self-destructive and sometimes hurt other people. Some demons may give their human host supernatural strength or other abilities that are used for destructive purposes. Aside from Jesus and, later, His disciples, demons often are quite difficult to remove.

The picture of a house now in order after the demon has left fits those descriptions. Instead of being out of control and destructive, the person free of demons returns to a normal and orderly existence.