Numbers 31:22-23

31:22 ‘Only the gold, the silver, the bronze, the iron, the tin, and the lead, 31:23 everything that may stand the fire, you are to pass through the fire, ¹  and it will be ceremonially clean, but it must still be purified with the water of purification. Anything that cannot withstand the fire you must pass through the water.

[31:23]  ¹ sn Purification by fire is unique to this event. Making these metallic objects “pass through the fire” was not only a way of purifying (burning off impurities), but it seems to be a dedicatory rite as well to the Lord and his people. The aspect of passing through the fire is one used by these pagans for child sacrifice.