"'When an evil spirit leaves a person, it goes into the desert, seeking rest but finding none. Then it says, "I will return to the person I came from." So it returns and finds its former home empty, swept, and in order. Then the spirit finds seven other spirits more evil than itself, and they all enter the person and live there. And so that person is worse off than before. That will be the experience of this evil generation.'"
We may seek to get sin out of our lives and be successful—for a while. However, unless we let Jesus in to fill "the empty space" with what he has to give us, we may end up worse off than before. Jesus' reference to "this evil generation" was in the context of the religious leaders asking for a sign. Their hearts were "empty, swept, and in order." That's not enough. There needs to be something inside that will leave no room for the evil spirits. Only Jesus can fill the whole space with life.