Jeremiah 6:28-30 New Revised Standard Version (NRSV)
28 They are all stubbornly rebellious,
going about with slanders;
they are bronze and iron,
all of them act corruptly.
29 The bellows blow fiercely,
the lead is consumed by the fire;
in vain the refining goes on,
for the wicked are not removed.
30 They are called “rejected silver,”
for the Lord has rejected them.