'Slag' in the Bible

You remove all the wicked of the earth like slag. Therefore I love your rules.

I will attack you; I will purify your metal with flux. I will remove all your slag.

"Son of man, the house of Israel has become slag to me. All of them are like bronze, tin, iron, and lead in the furnace; they are the worthless slag of silver.

Therefore this is what the sovereign Lord says: 'Because all of you have become slag, look out! -- I am about to gather you in the middle of Jerusalem.