And they shall know that I, the Lord, have not spoken in vain, that I would do this evil to them.
Other versions
King James Version
And they shall know that I am the LORD, and that I have not said in vain that I would do this evil unto them.English Standard Version
And they shall know that I am the LORD. I have not said in vain that I would do this evil to them."New International Version
And they will know that I am the LORD; I did not threaten in vain to bring this calamity on them.