Volkening was a revival preacher in Germany and he said the following:
On the other side of my garden fence grows an apple tree. Almost all the branches of the tree are hanging over the fence into my garden. It looks as if the tree belongs to my garden.
But the tree is outside. The tree is planted outside.
There are people who are giving the impression that they belong to the kingdom of God. They themselves are thinking that also.
But their roots are outside. They have not been transplanted into the garden of the Lord.
Pastor Wilhelm Busch is telling us about that in his book Licht vom unerschoepften Lichte on page 157.