Last week’s Parsha taught us the law concerning a כלי חרס, or earthenware utensil. If a קרבן was prepared in such a vessel, it has absorbed some of the parts of the sacrifice.
This vessel cannot be used again unless the absorbed taste is purged. This cannot be done in a כלי חרס, for once something is absorbed, purging does not help. The only remedy is to break such a vessel.
This is not the case with a כלי נחושת, a copper vessel. Purging does help with such a vessel as it will draw out what is absorbed.
It is similar regarding Pesach preparations. We are able to do הגעלה, which is the equivalent of purging, on wood, stone, and metal utensils, but not earthenware. Fire generally has the ability to draw out that which is absorbed. It is not the case with כלי חרס.
The site of the Mishkan in Shilo can be visited today, where broken pieces of כלי חרס from that period, are visible all around the area. Truly amazing!