Lo, when the wall is fallen, shall it not be said unto you, Where is the daubing wherewith ye have daubed it?
He confirms the last sentence, namely, that the false prophets would be a laughing-stock to all when their prophecies and divinations came to nothing, for the event would show them to be liars. For when the city was taken it sufficiently appeared that they were the devil’s ministers of deceit, for they were trained in wickedness and boldness when they put forth the name of God.
The false prophets seduce God's people by crying peace when there is no peace, comparing themselves to those who build a flimsy wall on sand. They cheat sinners by lessening their dread of sin and fear of God, telling idolaters there is neither harm nor danger in their way. This lends them a false authority until the storm comes and exposes the rottenness beneath.
AI summary
Commenting on Ezekiel 13:10-16
So will I break down the wall that ye have daubed with untempered mortar,.... Which is repeated and expressed in these words, both for the sake of confirmation and explanation of what is before said: and bring it down to the ground, so that the foundation thereof shall be discovered; meaning the city of Jerusalem, and by these phrases declaring the utter destruction of it...