This is the passage they refer to:
Return of an Unclean Spirit
“When the unclean spirit has gone out of a person, it passes through waterless places seeking rest, but finds none.
Then it says, ‘I will return to my house from which I came.’ And when it comes, it finds the house empty, swept, and put in order.
Then it goes and brings with it seven other spirits more evil than itself, and they enter and dwell there, and the last state of that person is worse than the first.
So also will it be with this evil generation.”
I want us to look at the last paragraph and note the words “this evil generation”.
He was referring to the generation of Jews of his day.
Jesus wasn’t teaching about demon possession. He was saying people who remain in the law, are like such people, who have been delivered from demons and then be invaded by more, when they have been told of the new covenant and still embrace or return to the old.
Peter says its like a “dog going back to its vomit”. Fortunately that ended in AD70 when the Law was destroyed.
Unfortunately, the Law still lingers in the consciousness of the believers’ mind. That’s how it’s like isn’t it?
Embrace grace. It’s over. There are no more demons to be cast out.