But disaster will come upon you; you will not know how to charm it away. A calamity will befall you that you will be unable to ward off. Devastation will happen to you suddenly and unexpectedly.
KJV
Therefore shall evil come upon thee; thou shalt not know from whence it riseth: and mischief shall fall upon thee; thou shalt not be able to put it off: and desolation shall come upon thee suddenly, [which] thou shalt not know.
ASV
Therefore shall evil come upon thee; thou shalt not know the dawning thereof: and mischief shall fall upon thee; thou shalt not be able to put it away: and desolation shall come upon thee suddenly, which thou knowest not.