Jeremiah 6:27-29

New International Version - UK

²⁷ ‘I have made you a tester of metals
    and my people the ore,
that you may observe
    and test their ways.
²⁸ They are all hardened rebels,
    going about to slander.
They are bronze and iron;
    they all act corruptly.
²⁹ The bellows blow fiercely
    to burn away the lead with fire,
but the refining goes on in vain;
    the wicked are not purged out.