R is for Refiner's Fire

Purify My Heart (Refiner's Fire) is a song by Brian Doerksen. I understand that the title is inspired from a number of pieces of scripture about refining - including the following:

Zechariah 13:7-9 (NIV)
‘Awake, sword, against my shepherd, against the man who is close to me!’ declares the Lord Almighty.
‘Strike the shepherd, and the sheep will be scattered, and I will turn my hand against the little ones.
In the whole land,’ declares the Lord, ‘two-thirds will be struck down and perish; yet one-third will be left in it.
This third I will put into the fire; I will refine them like silver and test them like gold.
They will call on my name and I will answer them;
I will say, “They are my people,” and they will say, “The Lord is our God.”’