Every thing that may abide the fire, ye shall make it go through the fire, and it shall be clean: nevertheless it shall be purified with the water of separation: and all that abideth not the fire ye shall make go through the water. The water of separation - The water in which the ashes of the red heifer were mingled; See Numbers 8:7 (note), Numbers 19:2 (note), etc. Garments, whether of cloth or skins, were to be washed. Gold, silver, brass, iron, tin, and lead, to pass through the fire, probably to be melted down.
Related Commentaries of Numbers 31:23
Numbers 31:23
23 Every thing that may abide the fire, ye shall make it go through the fire, and it shall be clean: nevertheless it shall be purified with the water of separation: and all that abideth not the fire ye shall make go through the water.