Jeremiah 6:28-30New International Version (NIV)
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.
30 They are called rejected silver,
because the Lord has rejected them.”